'... by analogy to the situation with calcitonin, it appears worthwhile to look for PTH in the brain and for physiological and behavioral effects of the hormone in the central nervous system' (Gennari, 1988) Introduction Parathyroid hormone (PTH)-like peptides, mRNA and degradative enzymes are present in hypophysiotropic regions of the hypothalamus, in which PTHbinding sites are located on neural membranes. Since exogenous PTH stimulates hypothalamic dopamine metabolism and the release of pituitary prolactin, PTH-like peptides in the hypothalamus may have neuroendocrine roles in the regulation of pituitary function. However, as PTH is produced peripherally and neurological disorders are symptomatic of hyperparathyroid disease states, parathyroidal PTH may also participate in the neuroendocrine control of the hypothalamo-pituitary axis. PTH in the hypothalamo-pituitary axis Unlike other peptides of the 'diffuse neuroendocrine system', PTH production was believed to be solely by the parathyroid gland (Rosenblatt et al. 1989), from which PTH