[Hypothyroidism caused by isolated TSH deficiency]. / Hypothyroïdie par déficit isolé en T.S.H.

Hypothyroidism secondary to isolated thyrotropin (TSH) deficiency was confirmed by low TSH levels during TRF test. Other anterior pituitary hormones were normal. Replacement therapy with thyroxine improved the child's growth but not the intellectual ability. The diagnostic difficulties and the importance of early treatment are emphasised.