The excessive production of GH in both the young and adult is due to adenomas consisting of somatotrophs. The main function of the hormone is to induce mammary gland growth and milk secretion in preparation for the suckling infant. The number and size of lactotrophs is dependent on oestrogen, particularly during pregnancy. The release of PRO rises during sleep in both sexes even though it appears to have no function in males. Prolactin secretion is under the control of both releasing and inhibiting hormones.
Dopamine is a powerful inhibitor of prolactin.
This hormone, as its name suggests controls the function of the adrenal cortex. It is a small polypeptide hormone of 39 amino acids which forms part of a large prohormone precursor whose processing also releases -endorphin, an endogenous opioid peptide. In the intermediate lobe the processing is different and alpha-MSH is formed. This substance can co-exist with vasopressin in some of the hypothalamic neurones that project to the median eminence. As its name suggests alpha-MSH acts on melanocytes to change pigmentation.