Is 1,25-Dihydroxyvitamin D Required for Reproduction?

Abstract

The role of 1,25-dihydroxyvitamin D (1,25-(OH)₂D) in avian and mammalian reproduction is examined. 1,25-Dihydroxyvitamin D is required, in both the avian and mammalian species, for maintenance of normocalcemia, adequate intestinal calcium absorption, bone turnover, and mineral homeostasis throughout the reproductive cycle— just as it is required in the nonlaying bird or nonpregnant, nonlactating mammal. In the avian species, 1,25-(OH)₂D is required for ovulation and shell formation, transfer of calcium from the egg shell across the chorioallantoic membrane to the fetal circulation, and maintenance of fetal serum calcium, bone metabolism, and mineral homeostasis. In the mammalian species, 1,25-(OH)₂D is required for normal ovulation, normal fetal and neonatal bone metabolism, milk production, and maintenance of normocalcemia and mineral homeostasis in the neonate. In the absence of 1,25-(OH)₂D, however, embryogenesis (rat and chick) and neonatal development (rat) can proceed in such a way as to produce viable, normal appearing offspring. The classical effects of 1,25-(OH)₂D deficiency (hypocacemia, inadequate intestinal calcium absorption, and bone mineralization) become increasingly apparent with advancing age but their are no other apparent major developmental abnormalities.