ABSTRACT
Subclinical hypothyroidism (SHypo) represents a condition of mild to moderate thyroid hormone deciency. It is characterized by normal thyroid hormones, although at the lower limits of their normal ranges, and mild or elevated serum TSH concentrations.1 In recent decades, the upper reference limit for TSH declined from 10 to 4.0 to 4.5 mIU/L. In the denition of SHypo, we distinguish patients with mildly increased serum TSH levels (5 to 9 mIU/L) and patients with more severely increased serum TSH levels (>10 mIU/L).
