Vitamin D: a steroid hormone with progesterone-like activity

Area of Science:

• Endocrinology
• Reproductive Biology
• Molecular Biology

Background:

• Vitamin D is recognized for its role in calcium homeostasis.
• Emerging evidence suggests broader physiological functions beyond bone health.
• Progesterone is a key hormone in the female reproductive system and pregnancy maintenance.

Purpose of the Study:

• To demonstrate the progesterone-like activity of calcitriol (1,25(OH)2D).
• To compare the in vivo and in vitro effects of progesterone and vitamin D.
• To investigate the role of vitamin D in the female reproductive system and pregnancy.

Main Methods:

• Literature review of English-language articles on vitamin D as a hormone (MEDLINE database).
• In silico analysis of steric structure similarities between progesterone and calcitriol.
• Utilized experimental structures from the RCSB Protein Data Bank for receptor-ligand complexes.

Main Results:

• Vitamin D exhibits physiological activities in early gestation, synchronized with progesterone.
• Vitamin D secretion increases during pregnancy, reinforcing progesterone's actions.
• Calcitriol enhances endometrial receptivity, supports implantation, and sustains pregnancy via pathways similar to progesterone.

Conclusions:

• Vitamin D acts as a steroid hormone with significant progesterone-like activity.
• Vitamin D and progesterone exhibit synergy, essential for successful pregnancy.
• Vitamin D is vital from the luteal phase onwards for reproductive success.