Endocrine Abstracts

Objectives: Iodine intake affects the risk of thyroid disorders. This study aimed to calculate the overall incidence of thyroid dysfunctions and structural abnormalities in the Faroe Islands and to describe the relation to sex and age.

Methods: We performed a nationwide, register-based study covering all 54,000 inhabitants of the Faroe Islands between 2006 and 2018. Cases were identified and classified by thyroid dysfunction using redeemed prescriptions of thyroid medication. We used a grace period of 19 months (2004-2006) to prevent recurrences of previous thyroid prescriptions. Structural abnormalities were diagnosed using ultrasonic examinations and thyroid scintigraphy available from 2008 to 2018. A patient chart review by a senior endocrinologist consultant confirmed all cases. Thyroid test results were available from all patients to support the classification of incident cases. ICD-10 diagnosis supported the diagnosis when available.

Results: We identified 1,152 individuals newly diagnosed with thyroid disease from 2006-2018, of which 990 (86%) cases received thyroid medication. The incidence of hypothyroidism was 112 per 100,000 person-years with a female:male ratio of 3:1, and 82% hosted a thyroid-peroxidase-autoantibody. The incidence of hypothyroidism increased with age in both women and men, and it decreased between 2008 and 2018 from 99 to 62 per 100,000 person-years (P < 0.001). The incidence of hyperthyroidism was 55 per 100,000 person-years with a female:male ratio of 3:1. Graves’ disease was the most frequent subtype of hyperthyroidism (49%), followed by multinodular toxic goitre (17%). Additionally, 11% were categorised as TSH-Receptor-Antibodies positive mixed type. Atoxic structural abnormalities (goitre, nodules, and cysts) were identified in 27 per 100,000 person-years, with a female-male ratio of 6:1. The occurrence of structural abnormalities was relatively stable throughout the study period.

Conclusions: A relatively high incidence of autoimmune thyroid disease was seen in the Faroese population. Results suggest that the pattern of thyroid disease is changing from that of iodine replete to iodine-deficient populations. The improved insight into the patterns and trends supports the work towards better care for those affected by thyroid disease. Our evaluation warrants continuous monitoring of thyroid disease occurrence among populations in the North Atlantic.