Hypothyroidism.

Hypothyroidism is a clinical entity first defined almost 100 years ago; it is caused, for the most part, by an autoimmune disorder or treatment of previous hyperthyroidism and so the vast majority have primary hypothyroidism. While the "textbook picture" does occur, the clinical findings in patients with mild to moderate disease are often nonspecific, particularly in the neonate and in the elderly. Diagnosis of primary hypothyroidism depends on showing that the serum TSH is elevated. Effective treatment, unchanged in principle since the 1890's, is best done with oral L-thyroxine. By using the serum TSH as well as the clinical findings as end-points, one can treat each patient individually.