Prolactin and thyrotrophin responses to thyroliberin (TRH) in patients with growth hormone deficiency: study in 167 patients

Both thyrotrophin (TSH) and prolactin (Prl) were studied under thyroliberin (TRH) stimulation tests in 167 hypopituitary dwarfs out of GH or T4 treatment. TSH and/or Prl responses were either low, normal or exaggerated and/or protracted. Various abnormal patterns were observed in most of the patients with low T4 but also in many patients with normal T4. The TSH response should be considered together with the value of T4. A normal response of TSH with a low T4 reflects a relative TSH deficiency from pituitary or hypothalamic origin. There was no clear relationship between the cause or type of hypopituitarism and the pattern of the responses of either TSH or Prl. The abnormalities of TSH and Prl were not related to each other except in patients with a past history of breech delivery. Then both TSH and Prl have to be measured after TRH in order to obtain full information from the test about hypothalamo-pituitary function. The frequency of the exaggerated and/or delayed or protracted responses of TSH and Prl with normal or low T4 is probably mostly related to hypothalamo-pituitary dysfunction. Abnormal responses of TSH or Prl, seldom of both hormones, were observed in otherwise isolated growth hormone (GH) deficiency, leading to a modification of such a diagnosis after the TRH test. Actually, the TRH test may be useful to ascertain the diagnosis of GH deficiency when the GH responses to provocative tests are borderline.