Combined pituitary function-test with four hypothalamic releasing hormones

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Abstract
Anterior pituitary function was investigated in ten healthy subjects by administering a combination of 200 µg thyrotropin releasing hormone (TRH), 100 µg gonadotropin releasing hormone (GnRH), 100 µg growth hormone releasing factor (GRF1–44), and 100 µg human corticotropin releasing factor (CRF). The same test protocol was performed in all subjects after pretreatment with 0.25 mg terguride. Five subjects were tested only with TRH and GnRH, five only with CRF, and six only with GRF. There was a prompt increase in all hormones after the administration of the four releasing hormones (RH). Pretreatment with terguride lowered the prolactin (PRL) increase (pp<0.05) compared with the test without dopamine agonist pretreatment. The PRL levels after combined RH administration were significantly higher than after TRH and GnRH alone. Although four of the five subjects had higher TSH levels after combined RH administration than after TRH and GnRH alone, the difference was not significant. Other hormones were not significantly influenced by the combined RH administration or dopamine agonist pretreatment. Despite the fact that the interaction of the different releasing hormones and dopamine agonists influences the pituitary hormone response, combined RH administration seems to be a useful test for evaluating pituitary function also in patients receiving dopamine agonist therapy.