| 1. |
- Lilja, Mikael
(författare)
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Trends in obesity and type 2 diabetes : ethnic aspects and links to adipokines
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Objective The prevalence of obesity and related diseases such as type 2 diabetes mellitus (T2DM) is increasing worldwide, and the Asian Indian population seems to be particularly susceptible to developing T2DM, even at a low body mass index (BMI). In Sweden, the age-adjusted prevalence of diabetes has not increased despite increasing self-reported obesity. However, modern data on the prevalence of obesity and T2DM in Scandinavia are absent.The biochemical links between obesity and subsequent T2DM are unknown, but the adipocyte-derived hormones leptin and adiponectin (adipokines) have been suggested as potential links because they both are related to insulin and glucose physiology. Some studies have found leptin to be an independent predictor of T2DM in men but not in women, although these results are inconsistent. In contrast, adiponectin has more consistently been linked to development of T2DM in both men and women. Furthermore, the leptin–adiponectin ratio may predict incident T2DM better than either of the two hormones separately.The aims of this thesis were to describe time trends in obesity and T2DM in northern Sweden, to evaluate leptin and adiponectin as predictors of deterioration in glucose metabolism including T2DM, and to evaluate leptin as a risk marker regarding ethnic differences, circ-annual variation, and intra-individual stability. Materials and methods Three large population surveys were used, the Northern Sweden MONICA (MONitoring of Trends and Determinants in CArdiovascular Disease) study, the Västerbotten Intervention Programme (VIP), and the Mauritius Non-Communicable Disease Study. Within the MONICA study, six cross-sectional surveys were performed in Sweden’s two northernmost counties, Norrbotten and Västerbotten, between 1986 and 2009. A total of 1000 men and 1000 women ages 25–64 years, also including from 1994 250 men and 250 women ages 65–74 years, were independently chosen for each survey. The overall participation rate was 75%. In 1999, a reinvestigation was performed in 74% of all participants from the three first surveys. Data from the MONICA surveys were used in papers I and IV and data from the reinvestigation survey in paper II. VIP is an ongoing population intervention program that started in the mid-eighties targeting cardiovascular risk factors and has covered the whole county of Västerbotten since 1991. Inhabitants are invited the years they turn 40, 50, and 60 years old, and the annual participation rate has varied between 48% and 67%. A subset (n=1780) from VIP was used in paper II for the circ-annual leptin analysis, and VIP data linked to the diabetes register in Västerbotten (DiabNorr) were used in a case referent study (640 patients with T2DM) in paper III. The Mauritius Non-Communicable Disease Study was performed in 1987 in 10 randomly selected (with probability proportional to size) population clusters. All eligible adults ages 25–74 years were invited, and the participation rate was 86% (n=5083). In 1992, a follow-up survey was performed in 49% of the initial participants. The Mauritius survey data were used in paper II. Results I. BMI increased in men ages 25–74 years and in women ages 25–44 years in northern Sweden between 1986 and 2004. The prevalence of obesity (BMI 30) increased in men ages 25–44 and 55–74 years and in women ages 25–44 years. The prevalence of obesity increased from 10.4% to 19.1% in men and from 12.9% to 17.9% in women ages 25–64 years. Waist circumference (WC) decreased in women of all ages and in men ages 55–64 years between 1986 and 1990. After 1990, WC increased again, and the prevalence of abdominal obesity rose markedly in women ages 25–64 years. II. Differences in circulating levels of leptin, leptin per BMI unit (leptin/BMI), and leptin per cm in WC (leptin/waist) were tested in men and women of Asian Indian, Creole (African), and Caucasian ethnicity. Asian Indian men and women had the highest leptin concentrations and Caucasian men and women the lowest while Creole men and women had intermediate values for leptin, leptin/BMI, and leptin/waist. No circ-annual variation in leptin concentrations was seen in Caucasians. The intra-individual test– retest stability for leptin was equal in men and women of different ethnicities, over 5–13 years, with an intra-class correlation of 0.65–0.82. III. High adiponectin concentrations predicted decreased risk of T2DM in both insulin-sensitive and insulin-resistant men and women, whereas high leptin levels predicted increased risk for T2DM only in insulinsensitive men. A high leptin–adiponectin ratio predicted T2DM in both men and women, and men with a high ratio had a shorter time to diagnosis than those with a low ratio. IV. In northern Sweden, fasting and post-load glucose increased in women ages 24–65 years with 0.2 mmol/l and 0.7 mmol/l, respectively, between 1990 and 2009. Consequently, the prevalence of impaired fasting glucose and impaired glucose tolerance (IGT) rose from 4.5% to 7.7%, and from 7.8% to 14.5%, respectively. In men, post-load glucose increased at 0.5 mmol/l, and the prevalence of IGT rose from 3.5% to 10.1%. The prevalence of diabetes did not increase. An independent relationship between leptin and changes in fasting and post-load glucose was seen in men but not in women. Conclusion An increasing obesity and concomitant deterioration in glucose metabolism was seen in northern Sweden in the period studied. High adiponectin concentrations predicted a decreased risk of T2DM in both men and women, whereas high leptin concentrations predicted an increase in fasting and post-load glucose as well as an increased risk of T2DM in men but not in women. Individual insulin resistance status modified the association between leptin and T2DM, and the leptin–adiponectin ratio may add further predictive information beyond the measures of the separate hormones. In relation to traditional anthropometric measures of obesity, Asian Indian men and women had the highest and Caucasians the lowest concentrations of leptin while Creole (African) men and women had intermediate levels. As a risk marker, leptin has a high intra-individual stability, equal in men and women and among different ethnicities over 5–13 years with no circ-annual variation.
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| 2. |
- Lindholm, Åsa Maria, 1958-
(författare)
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Metabolic Aspects in the Polycystic Ovary Syndrome
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders among women of childbearing age and is associated with a number of metabolic disturbances. It has been hypothesised these women carry an increased risk of developing cardiovascular diseases (CVD) with advancing age. The first aim of this thesis was to establish the prevalence of PCOS-related symptoms in Northern Sweden. The Northern part of the WHO MONICA project was used for this purpose. Based on self-reported menstrual disturbances and hirsutism together with biochemical analyses of free androgen index, the estimated prevalence of PCOS in Northern Sweden was 4.8%, which corresponded with previous prevalence studies. Disturbances in the fibrinolytic system are predictors of future cardiovascular events and measurements of plasminogen activator inhibitor 1 (PAI-1) activity and tissue plasminogen activator (tPA) mass concentration may be used to assess fibrinolytic activity in women with PCOS. From the findings, over-weight women with PCOS had impaired fibrinolysis, especially if they displayed objective biochemical markers of hyperandrogenism. Conversely, lean women with PCOS, displayed no signs of disturbed fibrinolysis. The adipose tissue is an active endocrine organ that produces and releases hormones, pro- and anti-inflammatory cytokines, and chemoattractant cytokines. Proinflammatory molecules produced by adipose tissue can be active participants in the development of insulin resistance and the increased risk of cardiovascular disease associated with obesity. The findings suggested being overweight, rather than the PCOS diagnosis per se, was the main explanatory variable for elevated adipose tissue inflammation in PCOS patients. Weight reduction is the primary target for intervention in overweight and obese women with PCOS. When this thesis was planned, no placebo-controlled trials on anti-obesity drugs in women with PCOS had been conducted. Sibutramine in combination with lifestyle intervention resulted in significant weight reduction in overweight women with PCOS. In addition to the weight loss, sibutramine appeared to have a beneficial effect on metabolic and cardiovascular risk factors.
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| 3. |
- Berhan, Yonas, 1970-
(författare)
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Epidemiological studies of childhood diabetes and important health complications to the disease
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background and aims: The overall aim of this thesis was to increase knowledge regarding the occurrence of childhood onset T1D and T2D in Sweden and in relation to that describe and elucidate important aspects on two grave complications to diabetes; end-stage renal disease (ESRD) and mortality. The two first studies included in this thesis aimed to describe and analyze the cumulative incidence of childhood onset T1D in Sweden and to assess the occurrence of undetected T2D in Swedish children. The aim with the third study was to describe the cumulative incidence of ESRD, and to analyze how ESRD risk differs with age at-onset and sex. The aim of the fourth study was to show how parental socioeconomic status (SES) affects all cause mortality in Swedish patients with childhood onset T1D.Study populations: The foundation for the studies on T1D was data from the Swedish Childhood Diabetes Registry (SCDR). When studying ESRD we also included adult onset T1D cases from the Diabetes Incidence Study in Sweden (DISS). The study on T2D was a population-based screening study where BMI was measured in 5528 school-children and hemoglobin A1c was measured in children with overweight according to international age and sex specific BMI cut-offs. To study ESRD and mortality, we linked the SCDR to various nationwide registers containing individual information on SES, mortality and ESRD.Results: The incidence rates of childhood onset T1D has continued to increase in Sweden 1977–2007. Age- and sex-specific incidence rates varied from 21.6 (95% CI 19.4–23.9) during 1978–1980 to 43.9 (95% CI 40.7– 47.3) during 2005–2007. Cumulative incidence by birth-cohorts has shifted to a younger age at-onset over the first 22 years of incidence registration. From the year 2000 there was a significant reverse in this trend (p<0.01). In contrast to the increase of T1D, we found no evidence of undetected T2D among Swedish school children. Despite a relatively high incidence in T1D in Sweden there is low cumulative incidence of ESRD, 3.3% at maximum 30 years of duration. We found difference between the sexes regarding long-term risk of developing ESRD that was dependent on the age at onset of T1D. When analyzing how socioeconomic status affects mortality in different age at death groups, we found that having parents that received income support increased mortality up to three times in those who died after 18 years of age.Conclusion: The incidence of childhood onset T1D continued to increase in Sweden 1978-2007. Between the years 1978-1999 there was a shift to a younger age at-onset, but from the year 2000 there is a change in this shift indicating a possible trend break. The prevalence of T2D among Swedish children up to 12 years of age is probably very low. There is still a low cumulative incidence of T1D associated ESRD in Sweden. The risk of developing ESRD depends on age at-onset of T1D, and there is a clear difference in risk between men and woman. Excess mortality among subjects with childhood onset T1D still exists, and low parental socioeconomic status additionally increased mortality in this group.
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| 4. |
- Brunström, Mattias, 1988-
(författare)
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Effect of antihypertensive treatment at different blood pressure levels
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- BackgroundHigh blood pressure is associated with an increased risk of cardiovascular disease and premature death. The shape of association between blood pressure and the risk of cardiovascular events is debated. Some researchers suggest that the association is linear or log-linear, whereas others suggest it is J-shaped. Randomized controlled trials of antihypertensive treatment have been successful in hypertension, but ambiguous in the high normal blood pressure range. Previous systematic reviews have not found any interaction between baseline systolic blood pressure and treatment effect, with beneficial effects at systolic blood pressure levels well below what is currently recommended. These reviews, however, use a method to standardize treatment effects and study weights according to within-trial blood pressure differences that may introduce bias.MethodsWe performed two systematic reviews to assess the effect of antihypertensive treatment on cardiovascular disease and mortality at different blood pressure levels. The first review was limited to people with diabetes mellitus. The second review included all patient categories except those with heart failure and acute myocardial infarction. Both reviews were designed with guidance from Cochrane Collaborations Handbook for Systematic Reviews of Interventions, and are reported according to PRISMA guidelines. We included randomized controlled trials assessing any antihypertensive agent against placebo or any blood pressure targets against each other. Results were combined in random-effects meta-analyses, stratified by baseline systolic blood pressure. Non-stratified analyses were performed for coronary heart disease trials and post-stroke trials. Interaction between blood pressure level and treatment effect was assessed with Cochran’s Q in the first review, and multivariable-adjusted metaregression in the second review.The third paper builds on data from the second paper, and assesses the effect of standardization according to within-trial blood pressure differences on the results of meta-analyses. We performed non-standardized analyses, analyses with standardized treatment effects, and analyses with standardized treatment effects and standard errors. We compared treatment effect measures and heterogeneity across different methods of standardization. We also compared treatment effect estimates between fixed-effects and random-effects meta-analyses within each method of standardization. Lastly, we assessed the association between number of events and study weights, using linear regression.ResultsForty-nine trials assessed the effect of antihypertensive treatment in people with diabetes mellitus. Treatment effect on cardiovascular mortality and myocardial infarction decreased with lower baseline systolic blood pressure. Treatment reduced the risk of death and cardiovascular disease if baseline systolic blood pressure was 140 mm Hg or higher. If baseline systolic blood pressure was below 140 mm Hg, however, treatment increased the risk of cardiovascular death by 15 % (0-32 %).Fifty-one trials assessed the effect of antihypertensive treatment in primary prevention. Treatment effect on cardiovascular mortality, major cardiovascular events, and heart failure decreased with lower baseline systolic blood pressure. If baseline systolic blood pressure was 160 mm Hg or higher treatment reduced the risk of major cardiovascular events by 22 % (95 % confidence interval 13-30 %). If systolic blood pressure was 140-159 mm Hg treatment reduced the risk by 12 % (4-20 %), whereas if systolic blood pressure was below 140 mm Hg, treatment effect was neutral (4 % increase to 10 % reduction). All-cause mortality was reduced if systolic blood pressure was 140 mm Hg or higher, with neutral effect at lower levels.Twelve trials compared antihypertensive treatment against placebo in people with coronary heart disease. Mean baseline systolic blood pressure was 138 mm Hg. Treatment reduced the risk of major cardiovascular events by 10 % (3-16 %), whereas the effect on mortality was neutral (7 % increase to 11 % reduction).Standardization of treatment effects resulted in more extreme effect estimates for individual trials. This caused increased between-study heterogeneity, and different results with fixed- and random-effects model. Standardization of standard errors shifted weights from trials with many events to trials with large blood pressure differences. This caused biased overall effect estimates. Standardization of standard errors also resulted in wider confidence intervals, masking the previously increased heterogeneity. This reduced the possibility to find different treatment effects at different blood pressure levels.Conclusion The effect of antihypertensive treatment depends on blood pressure level before treatment. Treatment reduces the risk of death and cardiovascular disease if baseline systolic blood pressure is 140 mm Hg or higher. Below this level, treatment is potentially harmful in people with diabetes, has neutral effect in primary prevention, but might offer additional protection in people with coronary heart disease. Standardization should generally be avoided in meta-analyses of antihypertensive treatment. Previous meta-analyses using standardized methods should be interpreted with caution.
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| 5. |
- Eriksson, Kerstin Margareta, 1955-
(författare)
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A 3-year lifestyle intervention in primary health care : effects on physical activity, cardiovascular risk factors, quality of life and cost-effectiveness
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: A sedentary lifestyle diminishes quality of life (QOL) and contributes to increasing prevalence of obesity, diabetes and cardiovascular diseases (CVD), and thus increases the economic burden on health care and society. Expensive and tightly controlled lifestyle interventions reduce cardiovascular risk and onset of diabetes. Transferring these findings to the primary care setting is of clinical importance. The primary aim of this thesis was to apply a lifestyle intervention program in the primary care setting among individuals with moderate-to-high risk for CVD, and evaluate the effects on physical activity, cardiovascular risk factor levels and QOL. A secondary aim was to investigate the cost-effectiveness. Methods: A randomized controlled trial with one intervention group (n=75) and one control group (n=76) with follow-up at 3, 12, 24 and 36 months was used. Patients with the diagnosis obesity, hypertension, dyslipidemia, type 2 diabetes or any combination thereof (mean age 54 yr, 57% female) were recruited from a primary health centre in northern Sweden. The three-month intervention period consisted of group-based supervised exercise sessions and diet counselling, followed by regular, but sparse, group meetings with a behavioural approach during three years. Clinical measurements included anthropometrics, aerobic fitness, blood pressure and metabolic traits. Questionnaires on self-reported physical activity, stages of change for physical activity, and QOL were used. In a cost-utility analysis the costs, gained quality-adjusted life years (QALY), and savings in health care were considered. Probability of cost-effectiveness was described using Net Monetary Benefit Method. Results: Overall, the lifestyle intervention generated beneficial improvements in anthropometrics, blood pressure, aerobic fitness and activity level, and QOL, compared to the control group which only received one information meeting. At 36 months, intention-to-treat analyses showed that lifestyle modification reduced waist circumference (–2.2 cm), waist-hip ratio (–0.02), systolic blood pressure (–5.1 mmHg), and diastolic blood pressure (–1.6 mmHg) and significantly improved aerobic fitness (5%). BMI, lipid or glucose values did not differ between groups. Progression to active stages of change for physical activity and increases in time spent exercising and total physical activity were reported. Both physical and mental dimensions of QOL were improved during the study period, but after 3 years differences persisted mainly in physical dimensions. Cost per gained QALY was low, 1668-4813 USD (savings not counted). Visits to family physicians significantly decreased and there was a net saving of 47 USD per participant. Probabilities of cost-effectiveness were 89-100% when 50 000 USD was used as threshold of willingness to pay for a gained QALY. Conclusions: A group-based lifestyle intervention program in a primary health care setting favourably influences cardiovascular risk-factor profiles, increases physical activity level, and improves several dimensions of QOL in high-risk individuals, at least up to 3 years. The intervention method was highly cost-effective in relation to standard care. The results emphasize the advantage of an intervention that combines supervised exercise with regular follow-ups for reaching long term effects. The study high-lights the feasibility of lifestyle interventions in the primary care setting and the importance of health care professionals supporting change in lifestyle.
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| 6. |
- Isaksson, Rose-Marie, 1964-
(författare)
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Symptoms, prehospital delay and long-term survival in men vs. women with myocardial infarction : a combined register and qualitative study
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The general aim of this thesis was to study symptoms, prehospital delay and time trends in long-term survival in men and women with myocardial infarction (MI). The study was based on quantitative and qualitative data collections. Study I was based on The Northern Sweden MONICA Myocardial Infarction Registry, 1989-2003, including 5072 men and 1470 women with a confirmed MI. Symptoms and prehospital delay were described and trends over time according to sex and age were studied. Typical pain was present in 86% of the men and 81% of the women and typical symptoms were more common among younger persons than older persons. Up to the age of 65 no gender differences were seen in the prehospital delay. In the oldest age group (65–74 years) time to hospital was longer than among the younger group, especially among women. Study II was based on individual interviews with 20 men with a first confirmed MI, representing the age range 65-80 years, about their experiences during the prehospital phase. The interviews were analyzed using qualitative content analysis. The interviewed older men described how the symptoms developed from diffuse ill-being, to a cluster of severe symptoms. The men had difficulties to relate to the experienced symptoms, which did not correspond to their expectations about an MI, and about whether they should seek medical care. By using different strategies the participants initially tried to understand, reduce, or treat the symptoms by themselves, with a desire to maintain an ordinary life. As the symptoms evolved to a persistent and alarming chest pain, the men realized the seriousness in the perceived symptoms, that all strategies were inefficacious and they came to the decision to seek medical care. Study III was based on individual interviews with 20 women with a first confirmed MI, representing the age range 65-80 years, about their experiences during the prehospital phase. The interviews were analyzed using qualitative content analysis. The interviewed older women described how the symptoms were perceived as a stepwise evolvement from intangible and bodily sensations to a more distinct, persistent and finally overwhelming chest pain. The women struggled against the symptoms and used different strategies, by downplaying and neglecting the symptoms in order to maintain control over their ordinary lives and maintain the social responsibilities. As the symptoms evolved to a persistent and overwhelming chest pain the women realized the seriousness in the perceived symptoms, they were not able to struggle against them anymore and they came to the decision to seek medical care. Study IV was based on The Northern Sweden MONICA Myocardial Infarction Registry which was linked to The Swedish National Cause of Death Registry for 6762 men and 1868 women, 25 to 64 years of age, with a first MI during 1985-2006. Also deaths before admission to hospital were included. Follow-up ended on August 30, 2008. Between 1985 and 2006 long-term survival after a first MI increased in both men and women. Over the whole 23-year period women showed a 9 percent higher survival then men. This slight difference was due to lower risk for women to die before reaching hospital, and during the last period similar rates of long time survival were noted in men and women. In conclusion there were no major differences between men and women in symptoms, prehospital delay or long-term survival. However, older patients had fewer typical symptoms and longer prehospital delay, especially among women. The prehospital phase was found to be multifaceted with experiences difficult to interpret in both men and women, with a dynamic development of symptoms, conceptions and expectations while the participants strove to maintain the ordinary and familiar life. The symptoms experienced presented a more heterogeneous and complex picture in both men and women than is usually described in the literature. Women under the age of 65 have a slightly higher age-adjusted long-term survival than men. Over a 23-year period long-term survival has improved similarly in both men and women.
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| 7. |
- Lieber, Ingrid, 1990-
(författare)
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Affective disorders and their treatments : implications for thyroid function
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- BackgroundThe relationship between affective disorders, mood-stabilisers and thyroid dysfunction is complex and poorly understood. Symptoms of thyroid dysfunction can overlap with symptoms of affective disorder, destabilise mood, and impact physical health. Subjective symptoms and biochemical abnormalities may not always match, especially when changes in thyroid function are only mild. Therefore, diagnosis and treatment of both hypothyroidism and hyperthyroidism in individuals with affective disorders remain complex. For lithium, a first-line treatment for bipolar disorder, an impact on thyroid function was first described in 1968. Since that time, it has become evident that lithium is much more frequently associated with hypothyroidism than hyperthyroidism. But even for lithium, many aspects of how associated thyroid dysfunction should be handled remain unclear. Aims The overall aim of this thesis was, in five studies, to examine aspects of the diagnosis and treatment of thyroid dysfunction in individuals with affective disorders, with a particular focus on lithium. The individual aims of the five studies were todetermine if lithium-associated hypothyroidism was reversible in individuals who had discontinued lithium.identify patterns and trends in thyroid hormone replacement therapy prescribed for individuals with bipolar or schizoaffective disorder.assess whether elevated thyroxine concentrations (hyperthyroxinaemia) were a risk factor for lithium intoxication caused by a change in tubular renal function.examine the incidence rate and aetiology of lithium-associated hyperthyroidism in individuals with bipolar or schizoaffective disorder.explore the attitudes of practising clinicians towards the diagnosis and treatment of subclinical hypothyroidism in individuals with or without affective disorder or anxiety.MethodsStudies 1–4 were part of the LiSIE (Lithium - Study into Effects and Side Effects) retrospective cohort study. LiSIE compares the effects and adverse effects of lithium treatment and other mood stabilisers in the Norrbotten Region and the Region of Västerbotten over a time period of up to 21 years between 1997–2017. For our studies, we used data from the Norrbotten Region only. Study 5 used a three-round modified Delphi consensus-building process. Study 5 was conducted with clinicians from three specialties, general practice, endocrinology and psychiatry, from two countries with similar health care systems, Sweden and the UK. ResultsStudy 1: Of 1340 potentially eligible individuals with lithium treatment, 90 individuals (who had developed hypothyroidism while treated with lithium and later discontinued lithium), were included. Of these, 27% had overt hypothyroidism at the start of thyroid hormone replacement therapy. Of the 85 individuals available for follow-up, 41% stopped thyroid hormone replacement therapy after lithium discontinuation. Only six individuals reinstated thyroid hormone replacement therapy subsequently. Only one had overt hypothyroidism.Study 2: Of 1564 potentially eligible individuals with bipolar or schizoaffective disorder, 291 (27%) had received thyroid hormone replacement therapy at some point during the 21-year review period. In 41% of cases, thyroid hormone replacement therapy was started for subclinical hypothyroidism. At the start of thyroid hormone replacement therapy, the median thyroid stimulating hormone (TSH) concentration was 6.0 (IQR 4.0) mIU/L. The median free serum thyroxine (fT4) was 11.8 (IQR 3.9) pmol/L. The median TSH concentration at the start of thyroid hormone replacement therapy decreased annually by 0.10 mIU/L, being significantly higher in individuals treated with lithium than in individuals treated with other mood stabilisers.Study 3: Of 1562 potentially eligible individuals with bipolar or schizoaffective disorder, 53 individuals had experienced a total of 65 episodes of unintentional lithium intoxication during the review period. In nine episodes, there was elevated fT4 at the time of lithium intoxication, corresponding to an incidence of 1.3 episodes/1000 person-years. For all nine episodes of unintentional lithium intoxication, we could identify alternative explanations that were more plausible than hyperthyroxinaemia. Study 4: In 1562 individuals with bipolar disorder or schizoaffective disorder, we identified 16 episodes of hyperthyroidism, corresponding to an incidence rate of 0.9 episodes/1000 person-years. Individuals who had concurrently been exposed to lithium, had an incidence rate of 1.3 episodes/1000 person-years. Individuals who had been previously exposed to lithium had an incidence rate of 0.8/1000 person-years. Individuals who had never been exposed to lithium (lithium naïve) had a 0.5/1000 person-years incidence rate. There were no significant differences in the risk ratios for individuals with concurrent or previous exposure compared to lithium-naïve individuals, neither for hyperthyroidism overall, nor for thyrotoxicosis or thyroiditis. Study 5: For the expert panel, 60 clinicians; 20 general practitioners, 20 endocrinologists and 20 psychiatrists were recruited. Fifty-three (88%) participants completed all three rounds. The participants reached a consensus on five of the 26 practice statements. The participants agreed that (a) repeated testing was required for the diagnosis of subclinical hypothyroidism, (b) antibody screening should usually occur, and (c and d) antibody screening would strengthen the indication for thyroid hormone replacement therapy in both individuals with and without affective disorder or anxiety. The participants disagreed with (e) requiring a TSH threshold of ≥ 20 mIU/L before starting thyroid hormone replacement therapy.ConclusionsStudy 1: In most cases, lithium-associated hypothyroidism appears reversible. Therefore, thyroid hormone replacement therapy could be discontinued more often once lithium is stopped. Study 2: In most cases, thyroid hormone replacement therapy was started with mild or absent thyroid function changes. The TSH level at which thyroid hormone replacement therapy was initiated decreased over time. When starting thyroid hormone replacement therapy for subclinical hypothyroidism in people with bipolar or schizoaffective disorder, clinicians must carefully weigh the benefits and risks.Study 3: Lithium intoxication with simultaneously elevated fT4 is uncommon. A direct causal link between elevated fT4 and altered tubular renal function remains elusive. An increased frequency of routine thyroid function tests is unlikely to decrease the risk of lithium intoxication. Study 4: Lithium-associated hyperthyroidism is uncommon. The risk of hyperthyroidism does not differ significantly between lithium-exposed and lithium-naïve individuals.Study 5: Attitudes toward diagnosing and treating subclinical hypothyroidism remain diverse. A threshold of an TSH of at least 20 mIU/L for thyroid hormone replacement therapy start, suggested in a previously published guideline, was deemed too high. As the evidence regarding diagnosis and treatment of subclinical hypothyroidism remains limited, future guidelines should consider the views of a broad range of practising clinicians to increase their clinical acceptability and usefulness.
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| 8. |
- Mayans, Sofia, 1976-
(författare)
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Genetic studies of diabetes in northern Sweden
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Diabetes mellitus represents a group of metabolic disorders caused by both environmental and genetic factors. The two most common forms of diabetes are type 2 diabetes (T2D) and type 1 diabetes (T1D). T2D is associated with obesity and the disease is caused by insulin resistance and pancreatic b-cell dysfunction. T1D is an autoimmune disease in which the insulin- producing b-cells in the pancreas are destroyed by infiltration of lymphocytes. The aim of this thesis was to identify genes conferring susceptibility to diabetes. This was approached using genetic methods, both linkage and association studies, within the population of northern Sweden. The northern Swedish population is well suited for genetic studies of familial forms of disease, since an internal expansion of the northern Swedish population, coupled with a low frequency of immigration and a high frequency of consanguineous marriages, has resulted in a relatively homogeneous gene pool. This simplified genetic background increases the probability of identifying genes contributing to disease. The family-based material used for the type 2 diabetes studies (papers I and II) consisted of 231 individuals from 59 families originating in northern Sweden. The type 2 diabetes case-control material (papers I and II) consisted of 872 cases and 857 matched controls, all from northern Sweden. In paper I we performed a genome-wide linkage scan, seeking T2D susceptibility loci. Linkage to the previously identified Calpain-10 region was found, however, association studies in the case-control material revealed no association to the CAPN10 gene. Using both the family-based and the case-control material, we were able to confirm the association of polymorphisms in the TCF7L2 gene to T2D in the population of northern Sweden (paper II). CTLA-4 is a negative regulator of T cell activity, belonging to the CD28 co-stimulatory receptor family. Numerous reports, including our own, have associated CTLA-4 variants with T1D as well as other autoimmune diseases, such as autoimmune thyroid disease (AITD). Allelic variation in the 3ÚTR of the CTLA-4 gene was associated to human T1D and this variant has also been suggested to affect the level of mRNA encoding the soluble form of the molecule (sCTLA-4). We confirmed the association of allelic variation in the 3ÚTR of the CTLA-4 gene in a T1D/AITD case-control material from northern Sweden, consisting of 104 individuals with ATID, 149 individuals with T1D and 865 matched controls. However, we were unable to identify any correlation between allelic variants in the 3ÚTR of the CTLA-4 gene and expression of sCTLA-4 (paper III). Based on recently published genome-wide association (GWA) scans, 33 single-nucleotide polymorphisms (SNPs) located within 16 genes were selected for an association analysis in T1D/AITD families from northern Sweden. The T1D/AITD family-based material consisted of 253 cases and 206 healthy individuals from 97 northern Swedish families. Analysis revealed association to T1D for SNPs in PTPN22, COL1A2, IL-2Ra and INS. In addition, SNPs in CTLA-4, IL-2 and C12orf30 were shown to be associated to AITD (paper IV). Together, these results underpin the notion that the population of northern Sweden is well suited for the detection of genes involved in complex diseases. The use of our more restricted patient material, compared to materials used in published GWA scans, enables the discovery of disease associated genes in a more cost effective manner and show that our population is capable of detecting general susceptibility genes.
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