Effect of calcitonin and 1,25(OH)2-vitamin D3 on the FSH, LH and testosterone secretion at rest and LHRH stimulated secretion.

The calcium signal plays an important role in the control of the secretory process of some adenohypophyseal hormones which responds to the administration of calciotropic substances by a marked change. In the submitted work the effect of calcitonin and 1,25(OH)2-vitamin D3 (1,25(OH)2D3) on FSH, LH and testosterone secretion was investigated. A single dose of 50 U synthetic salmon calcitonin did not influence the FSH, LH and testosterone secretion at rest nor stimulated secretion. 1,25(OH)2D3 administered for four days in amounts of 3 micrograms/day did not affect the LH and testosterone secretion but increased slightly the secretory response of FSH to LHRH, significantly during the 80th minute following administration of the secretagogue (P less than 0.01). The indication of bi-phasic FSH secretion was eliminated by 1,25(OH)2D3. The significant decline of PTH levels following administration of 1,25(OH)2D3 is evidence of a biologically effective level of 1,25(OH)2D3 attained by the administered dose of hormone. As compared with the marked effect of calcitonin and 1,25(OH)2D3 on thyrotropic hormone secretion, it may be concluded that the gonadotropic system is considerably less sensitive to a change of calcium homeostasis induced by calcitonin or 1,25(OH)2D3. Nevertheless a slight increase of the FSH secretion and a change of the dynamics of its secretion suggest a modulating role of 1,25(OH)2D3 in the control of FSH secretion.