The role of opiate, dopaminergic, and adrenergic systems in the hypothalamo-pituitary dysfunction in obesity

In order to evaluate the role of opiate, dopaminergic and adrenergic systems in the mechanism of hypothalamo-pituitary disturbances in obesity, 9 obese women and 14 healthy women were investigated. Serum GH, LH, beta-endorphin and cortisol concentrations were measured after administration of clonidine, an alpha 2-adrenergic receptor agonist, and naloxone, an opiate antagonist. Additionally, PRL levels were measured after administration of the dopamine receptor blocker metoclopramide. An impaired GH response to clonidine and naloxone was found in obese women. However, a marked increase in beta-endorphin was observed in obese patients after clonidine administration. Naloxone did not cause any significant change in beta-endorphin release. Neither clonidine nor naloxone induced any change in LH release. Serum PRL concentrations in response to metoclopramide were significantly higher in obese patients than in healthy women.

Disturbed activity in opiate, adrenergic, and dopaminergic systems may be of pathogenetic importance in a hypothalamo-pituitary dysfunction in obesity. The occurrence of hypothalamic amenorrhoea as well as the presence of abnormalities of the central nervous system regulation of GH, PRL, ACTH, cortisol, insulin and vasopressin output might point to a generalized hypothalamo-pituitary dysfunction in obesity.