Serum thyroid stimulating hormone in assessment of severity of tissue hypothyroidism in patients with overt primary thyroid failure: cross sectional survey

Primary hypothyroidism is a graded phenomenon with a wide spectrum of severity between subclinical hypothyroidism and overt hypothyroidism. Patients with biochemically severe hypothyroidism may present with only mild clinical manifestations, whereas some patients with moderate changes in thyroid hormones may present with severe signs of tissue hypothyroidism.1 The measurement of pituitary thyroid stimulating hormone (TSH) is the most sensitive test for early diagnosis of primary hypothyroidism. The magnitude of elevation of TSH is commonly believed to correspond to the severity of tissue hypothyroidism. We aimed to evaluate the value of measuring serum TSH in assessing the severity of tissue hypothyroidism in patients with overt hypothyroidism. We recruited 49 patients with overt hypothyroidism (TSH >20 mU/l, free thyroxine