Does calcitonin modulate anterior pituitary hormone secretion?

In a group of 5 healthy subjects salmon CT (sCT) infusion was unable to induce significant variations on basal secretory levels of LH, FSH, PRL and TSH. In a second group of 5 normal subjects, GnRH and TRH tests were performed both during sCT and saline infusion; a clear inhibition of TSH-stimulated levels and of PRL area was documented, while gonadotropin secretion was not significantly affected by sCT infusion. These results suggest that CT effect might be attributed to a change in intracellular calcium of pituitary cells; however the different behavior between TRH-and GnRH-stimulated hormones might be due to a different hormonal release mechanism. Furthermore the widespread recognition of CT-like immunoreactivity in adenohypophysis and in portions of the central nervous system suggests that CT may be a neurotransmitter or paracrine regulator.