Prevalence of various degrees of hypothyroidism among patients of a general medical department.

We have measured basal thyrotropin (TSH) in 945 consecutive patients of a general medical department. Additional thyroid tests were carried out in patients with elevated TSH. Thirty patients (3.1%) had subclinical hypothyroidism, i.e. an elevated TSH with no clinical signs and with a normal free thyroxine index. A cause was found in only fifteen of these thirty patients. Thirteen additional patients (1.37%) had mild or overt primary hypothyroidism, three of which were already diagnosed. This prevalence is three times higher than that found in a retrospective survey at the same hospital. Of the ten newly-detected cases five were discharged on thyroid hormone replacement. In two patients the antithyroid drugs which were the cause of hypothyroidism were discontinued. The remaining three patients had severe non-thyroidal illnesses and thyroid hormone was not prescribed. A cause for the hypothyroidism (autoimmune thyroid disease, post-radioiodine, post-thyroidectomy or antithyroid drugs) was established in all but two cases. The data suggest that thyroid function tests (preferably a TSH) should be performed on any patient with prior treatment to the thyroid and, in addition with very broad indications, perhaps even routinely, in all women over 50 years of age.