Normal serum concentrations of sex hormone binding-globulin in patients with hyperthyroidism due to subacute thyroiditis

Serum concentrations of sex hormone binding-globulin (SHBG) were determined in patients with hyperthyroidism (n = 94; 12 men, 82 women) due to either Graves' disease (n = 59; 11 men, 48 women), autonomous thyroid adenomas (n = 23; 1 man, 22 women), or subacute thyroiditis (n = 12; all women). Elevat ed serum concentrations of SHBG were initially seen in 57 of 82 patients (6 9%) with hyperthyroidism due to either Graves's disease or due to autonomou s adenoma. Elevated serum SHBG concentration was more frequent in patients with serum total thyroxine (TT4) concentrations greater than 15.0 mu g/dL ( 32/39 [82%]; including 3 patients with autonomous adenoma) compared to thos e with serum TT4 concentration between 11.0 and 15.0 mu g/dL (21/27 [77%]; including 7 patients with autonomous adenoma), or patients with an isolated elevation of serum total triiodothyronine (TT3) concentration (4/16 [25%]; including 2 patients with autonomous adenoma). Serum SHBG concentration no rmalized when patients became euthyroid. Only 1 of 12 patients in the hyper thyroid phase of subacute thyroiditis had an elevated serum concentration o f SHBG. Serum concentrations of thyroid binding globulin (TBG) and transcor tin (CBG) were normal in all but 1 patient. In patients with hyperthyroidis m as a result of Graves' disease or autonomous adenoma serum SHBG concentra tions were elevated with the greatest elevation found in patients with the highest serum T-4 concentrations. The normal concentrations of SHBG in the hyperthyroid phase of subacute thyroiditis most likely reflects the shorter duration of exposure to increased thyroid hormone in this condition.