[Increased prolactin concentration and thyrotropic insufficiency in patients with growth hormone deficiency]

An increase in TSH secretion in patients with growth hormone deficiency (GHD) indicates hypothalamic thyrotropic dysfunction. A simultaneous increase in prolactin (PRL) response to TRH is often observed in these patients. In order to find out whether these patients need additional thyroxine treatment, we investigated thyrotropic function in 15 patients with GHD and increased PRL secretion. 3 groups of patients emerged: 1. Four patients were clinically hypothyroid (T42.9 +/- 1.3 micrograms/dl); 2. Four patients developed low T4 levels during growth hormone therapy (T43.5 +/- 0.1 micrograms/dl), although their T4 levels were normal before growth hormone treatment was initiated (T45.7 +/- 0.5 micrograms/dl). 3. Seven patients had T4 levels in the lower normal range (7.0 +/- 0.8 micrograms/dl). The growth velocity of these patients was monitored when thyroxine treatment was given in addition to hGH. Thyroxine administration resulted in suppression of TSH secretion in all patients while PRL concentrations remained elevated. Growth velocity was improved with additional T4 therapy in groups 2 and 3 without undue acceleration of bone age. All patients with GHD and elevated PRL levels should be carefully monitored for thyrotropic dysfunction.