Thyroid autoimmunity in Greenlandic Inuit

Objective

This study aimed to provide the first data on the occurrence of thyroid autoimmunity among Inuit in Greenland, a distinct ethnic group who is not iodine deficient.

Design

This study is a population-based cross-sectional study.

Methods

Data were collected in Nuuk in West Greenland and in Ammassalik district in East Greenland. Information on lifestyle, diet and diseases was obtained using questionnaires. Thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb) and thyroid-stimulating hormone (TSH) were measured in serum. Iodine and creatinine were measured in spot urine samples.

Results

The participation rate was 95% with 434 Inuit participants; 75% were smokers. Iodine excretion was 169 µg/24 h in urban West Greenland, 224 µg/24 h in the main town and 228 µg/24 h in settlements in rural East Greenland. TPOAb, TgAb or either of these was measured in the serum from 3.7, 5.9 and 8.3% of participants, respectively. TPOAb or TgAb was found in 9.3% of Inuit women and 7.5% of men and more frequently, in East Greenland Inuit with the higher iodine excretion (P = 0.02). There was some evidence suggesting that thyroid autoimmunity was more frequent among non-smokers (12.5%) compared to smokers (7.0%). Harbouring a thyroid autoantibody was most frequent in participants with TSH above 3.6 mIU/L (P < 0.001).

Conclusion

Thyroid autoantibodies were rare among Greenland Inuit. While iodine nutrition was associated with autoimmunity similarly to other ethnic groups, the influence of sex and smoking was limited. This could suggest genetic component in Inuit, but the impact of cold, selenium and persistent organic pollutants needs to be elucidated.

Non-alcoholic fatty liver disease in patients with type 2 diabetes in Greenland: a register-based cross-sectional study

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide due to its close association to the metabolic syndrome of type 2 diabetes mellitus (T2DM), obesity and insulin resistance. However, the prevalence and severity of NAFLD in Greenland remain unexplored. We aimed to estimate the prevalence of liver steatosis and fibrosis among Greenlanders and Danes with T2DM living in Greenland using biochemical surrogate markers. We included 1409 Greenlanders and 182 Danes with T2DM in this register-based cross-sectional study. Greenlanders had higher BMI and plasma lipid levels and lower HbA1c levels compared with Danes (p<0.05). Their median alanine aminotransferase (ALAT) levels were similar. However, more Greenlanders had elevated ALAT levels (20.5% vs. 11.5%, p<0.05). Greenlanders had lower FIB-4 scores than Danes, 0.91 (IQR: 0.66–1.27) vs. 0.97 (IQR: 0.78–1.34), without difference in FIB-4 score categories (p=0.27). The prevalence of advanced fibrosis was low in both populations (1.7–2.6%). In conclusion, Greenlanders with T2DM had better glycaemic control despite higher BMI and plasma lipids. A larger proportion of Greenlanders had elevated plasma ALAT levels, while FIB-4 scores were lower than Danes. These findings suggest that Greenlanders with T2DM may be less likely to develop liver complications than Danes with T2DM in Greenland.

Adaptation to a High Iodine Intake in Greenland Inuit Suggested by Thyroid Disease Pattern

Objective: Arctic living is influenced by cold winters, short summers, and excessive iodine intake from the traditional Inuit diet providing for habitation of the Arctic for centuries. This is changing and we surveyed thyroid function in populations living in Greenland. Design: Population-based cross-sectional study. Methods: Data were collected in the capital city in West Greenland and in rural East Greenland. Information on lifestyle, dietary habits, and medical history was obtained using questionnaires. Thyrotropin, free thyroxine, free triiodothyronine, thyroglobulin, and thyroglobulin antibody were measured in serum, iodine, and creatinine in spot urine samples. Results: One percent of the Greenlandic population was invited and 535 participated with an overall participation rate of 95%. Iodine excretion was 225 μg/24 hours in East Greenland and 169 μg/24 hours among West Greenland Inuit. Hyperthyroidism occurred in 10.7% of West Greenlandic Inuit (men/women: 4.3%/16.3%) and 7.8% of East Greenlandic Inuit (3.8%/12.8%). Hypothyroidism was found in 2.7% in West Greenland (0.0%/5.0%) and 5.6% (5.6%/5.6%) in East Greenland. Conclusion: Hyperthyroidism was frequent among Inuit and the occurrence of hypothyroidism was low. The pattern of hyper- and hypothyroidism among Greenlandic Inuit with adequate iodine intake was comparable with those seen in populations with iodine deficiency. Inuit may thus have adapted to excessive iodine intake over centuries, causing a need for a higher iodine intake to prevent iodine deficiency disorders.

Low prevalence of retinopathy among Greenland Inuit

To assess the prevalence of diabetic retinopathy (DR) among persons with diabetes and prediabetes participating in the 2018 Population Health Survey in Greenland (B2018), a follow-up survey of three previous health surveys. Participants were invited to a diabetes complication screening. We assessed the prevalence of DR using Optos Daytona Ultra-wide field fundus camera and assessed differences in prevalence according to demographic and clinical characteristics using chi square test and a t-test and assessed DR based on ethnicity. The overall prevalence of DR was 2% (10/483). Among participants with HbA₁c ≥48 mmol/mol (6.5%) DR prevalence was 9% (9/91), compared with <1% (1/382) among participants with HbA₁c <48 mmol/mol (6.5%). All participants with DR lived in towns. The mean Inuit genetic admixture was lower among participants with DR. The prevalence of DR is low in Greenland and almost non-existent among persons with HbA₁c below the diabetes threshold.

Ethnicity is important for creatinine excretion among Inuit and Caucasians in Greenland

BACKGROUND

Human nutrition, contamination and renal function are commonly assessed by the analysis of urine. A complete 24-hour urine sample is the ideal but it is inconvenient and unreliable. Thus, spot urine sampling with creatinine adjustment is widely used. Stratification for age and gender is recommended. Still, ethnicity may influence creatinine excretion.

METHODS

We collected 104 24-h urine samples among Inuit and non-Inuit living in Greenland. Completeness of sampling was checked by using para-amino benzoic acid (PABA) that also allowed for compensation of creatinine excretion when sampling was incomplete. We measured creatinine using the Jaffe method and PABA by the HPLC method.

RESULTS

Participants were recruited from the capital city, a major town and a settlement (n = 36/48/20). They were aged 30-69 years with 78 Inuit and 26 non-Inuit. Inuit were smaller than non-Inuit (Caucasians): height, 163 vs. 177 cm, p < 0.001; weight, 71 vs. 84 kg, p = 0.001 with similar BMI. Creatinine excretion was lower in Inuit compared to non-Inuit (men, 1344/1807 mg/24 h; women 894/1259 mg/24 h; p = 0.002; 0.02). It was influenced by age (p < 0.001), gender (p < 0.001), weight (p = 0.001) and ethnicity (p = 0.030) while not by the intake of the protein-rich Inuit diet in the adjusted analysis. Creatinine excretion was described by: Inuit men, 1925 mg - (13.1 × age); Inuit women, 1701 mg - (17.0 × age).

CONCLUSION

Inuit and Caucasians have different creatinine excretion. It is recommended to stratify by ethnicity in addition to adjustment for age and gender when using creatinine correction of spot urine samples.

Raised BMI cut-off for overweight in Greenland Inuit--a review

Background

Obesity is associated with increased morbidity and premature death. Obesity rates have increased worldwide and the WHO recommends monitoring. A steep rise in body mass index (BMI), a measure of adiposity, was detected in Greenland from 1963 to 1998. Interestingly, the BMI starting point was in the overweight range. This is not conceivable in a disease-free, physically active, pre-western hunter population.

Objective

This led us to reconsider the cut-off point for overweight among Inuit in Greenland.

Design and findings

We found 3 different approaches to defining the cut-off point of high BMI in Inuit. First, the contribution to the height by the torso compared to the legs is relatively high. This causes relatively more kilograms per centimetre of height that increases the BMI by approximately 10% compared to Caucasian whites. Second, defining the cut-off by the upper 90-percentile of BMI from height and weight in healthy young Inuit surveyed in 1963 estimated the cut-off point to be around 10% higher compared to Caucasians. Third, if similar LDL-cholesterol and triglycerides are assumed for a certain BMI in Caucasians, the corresponding BMI in Inuit in both Greenland and Canada is around 10% higher. However, genetic admixture of Greenland Inuit and Caucasian Danes will influence this difference and hamper a clear distinction with time.

Conclusion

Defining overweight according to the WHO cut-off of a BMI above 25 kg/m² in Greenland Inuit may overestimate the number of individuals with elevated BMI.

Clinical risk factors for osteoporosis are common among elderly people in Nuuk, Greenland

Background

Osteoporosis is a debilitating condition characterized by fractures, pain and premature death. Risk factors for osteoporosis predict the risk of fragility fractures.

Aim

To describe the occurrence of risk factors for osteoporosis among populations in Nuuk, the capital of Greenland.

Methods

A random sample of women born in 1934–42, 1945–47, 1956, and men born in 1956 were selected from the national civil registry. A questionnaire was sent out in Greenlandic and Danish on risk factors for osteoporosis: family history, smoking habits, alcohol intake, presence of disease, sun exposure, intake of dairy products, age at menopause (women) and number of falls. Additional questions included the frequency of back pain, previous fractures, intake of vitamin D and calcium supplements, use of anti-osteoporotic drugs, steroids and other drugs.

Results

The questionnaire was sent to 317 subjects confirmed to be living at an address in Nuuk and 181 (57.1%) responded. More young women than older women were smokers (60.6% vs. 35.0%; p=0.022) while limited sun exposure was reported by more of the old women (37.2% vs. 5.6%; p=0.003). Family history of osteoporosis was reported by 15.0%, without difference between groups. Alcohol and milk intake did not differ between groups. Premature menopause was reported by 17.9% of the women. Falls within the last year were reported by 42.4% with fewer falls in the oldest age group (21.9% vs. 50.0%; p=0.005). Frequency of fragility fractures increased with age (5.7% vs. 24.3% vs. 30.4%; p=0.02) and the risk of a fragility fracture increased with age (p=0.004; OR, 95% CI: 4.5, 1.6–12.2, reference: below 70 years), when adjusted for smoking, gender and falls. The use of anti-osteoporotic drugs was low (3.4%) while 28.8% took calcium and vitamin D supplements.

Conclusions

Age is a dominating risk factor for fragility fractures in Greenland. The use of anti-osteoporotic drugs is low in Greenland, even if osteoporotic fractures are common in old age.