Endocrine Abstracts

Introduction: Thyroid disease, both clinical and subclinical, is a common disorder. Various studies, however, differ in reported prevalences of abnormal thyroid function.

Aim of the study: To investigate 1. the prevalence of abnormal thyroid function and anti-thyroidperoxidase antibodies (TPOab) in a random sample of the inhabitants of a middle-sized city in the Netherlands; 2. the relationship of the presence of TPOab with TSH concentration in the euthyroid range; and 3. the relationship of positive TPOab and incidence of thyroid dysfunction.

Methods: 2703 adult inhabitants of the city of Groningen, the Netherlands, participated in this prospective population survey. Details about the use of thyroid hormone replacement therapy (THRT) and thyroid blocking agents were present in 2611 subjects. Incidence of thyroid disease was determined from a questionnaire taken 5 years after the baseline visit. TSH (reference range 0.35–4.94 mIU/L) and FT4 (reference range 9.14–23.81 pmol/L) were determined using a microparticle enzyme immunoassay (Architect and AxSYM respectively) at baseline.

Results: 1.4% of 2611 subjects used thyroid medication (age 58±12 yrs; 70% female), mostly THRT. Of all the subjects not taking thyroid medication 2.0% had increased TSH and 2.4% decreased TSH. TPOab were present in 10.5% of 2703 subjects, with highest prevalence in older women (23% in women aged 56–65 yrs). Prevalence of TPOab increased with higher TSH, up to 50% in subjects with the highest TSH levels in the euthyroid range. Incidence of thyroid disease after 5 years of follow-up ranged from 1% in TPOab negative subjects with low normal TSH concentration to 25% in TPOab positive subjects with the highest TSH levels in the euthyroid range.

Conclusion: The prevalence of abnormal thyroid function in the general population is substantial. Even in the euthyroid range, presence of TPOab is positively correlated with TSH concentration, and associated with future thyroid disease.