Dopamine in the pituitary adaptation to starvation in man

To investigate the role of the dopaminergic system in the pituitary adaptation to energy deprivation, the effect of metoclopramide, a dopamine receptor blocker, on prolactin (PRL), TSH, FSH and LH secretion was investigated in 6 healthy men in the fed state and at 36 h starvation. All underwent a further 36 h of starvation on a separate occasion to assess the effect of starvation on the TSH and PRL responses to TRH and the LH and FSH responses to gonadotrophin releasing hormone (GnRH). In all subjects starvation produced the expected reduction in serum T3 and an average decrease of 53% in the cumulative TSH response to TRH. The basal serum PRL and its response to TRH and metoclopramide remained unchanged with 36 h starvation. The FSH response to GnRH also remained unchanged, but the LH response was significantly greater during starvation. We conclude that factor(s) other than dopamine influence not only thyrotrophic activity but also other aspects of pituitary function during energy deprivation.