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). Elevated serum concentrations of SHBG were initially seen in 57 of 82 patients (69%) with
hyperthyroidism due to either Graves's disease or due to autonomous
adenoma. Elevated serum SHBG concentration was more frequent in patients with serum total
thyroxine (TT4) concentrations greater than 15.0 microg/dL (32/39 [82%]; including 3 patients with autonomous
adenoma) compared to those with serum TT4 concentration between 11.0 and 15.0 microg/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 normalized when patients became euthyroid. Only 1 of 12 patients in the
hyperthyroid phase of
subacute thyroiditis had an elevated serum concentration of SHBG. Serum concentrations of thyroid binding
globulin (TBG) and
transcortin (
CBG) were normal in all but 1 patient. In patients with
hyperthyroidism as a result of
Graves' disease or autonomous
adenoma serum SHBG concentrations were elevated with the greatest elevation found in patients with the highest serum T4 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.