Transitory subclinical and permanent hypothyroidism in the course of subacute thyroiditis (de Quervain)

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Abstract
Sixty-two patients affected with subacute thyroiditis (SAT) were followed for a mean period of 14 mo. (range 1-40), by monitoring thyroid hormone levels in basal condition, pituitary TSH reserve, antithyroglobulin (TgAb) and antimicrosomal antibodies (MsAb), in order to study the natural course of the disease and to characterize its intermediate phase. In the 1st phase the mean serum iodothyronine levels were within normal limits, nevertheless elevated triiodothyronine [T3] and thyroxine [T4] levels were detected in 34 (54%) and 20 (32%) patients, respectively. The next phase was characterized by normal serum iodothyronine levels; TRH stimulation test, however, showed a significant increase of pituitary TSH reserve in 35 (56%) patients. All parameters reverted gradually towards normal in all but 3 patients, who showed overt permanent hypothyroidism. TgAb and MsAb were positive in the early stage in 15 (24%) and 40 (64%) patients, respectively, disappearing at the end of the follow-up period in all but 1 patient; this particular patient belonged to the group of 3 patients affected with permanent hypothyroidism. The onset of SAT is characterized by transient hyperthyroidism. Transient subclinical hypothyroidism characterizes the next phase. TRH stimulation test is required for the diagnosis of the latter and for the identification of the few who develop permanent hypothyroidism.