Pregnancy as state of physiologic absorptive hypercalciuria

Area of Science:

• Endocrinology
• Nutritional Science
• Obstetrics

Background:

• Pregnancy increases 1,25-dihydroxyvitamin D and calcium absorption, typically viewed as compensatory for fetal needs.
• The possibility that these changes anticipate fetal demands has not been explored.

Purpose of the Study:

• To investigate the impact of pregnancy on intestinal calcium absorption and renal calcium excretion.
• To assess changes in 1,25-dihydroxyvitamin D and parathyroid function during pregnancy.

Main Methods:

• 16 healthy women underwent oral calcium tolerance tests during and after pregnancy.
• Urinary calcium excretion, circulating 1,25-dihydroxyvitamin D, and parathyroid function were measured.

Main Results:

• 1,25-dihydroxyvitamin D levels were significantly elevated throughout pregnancy compared to postpartum.
• Urinary calcium excretion increased substantially during pregnancy, often resulting in hypercalciuria.
• Calcium tolerance tests showed increased calciuric and calcemic responses during pregnancy; fasting excretion and parathyroid function remained normal.

Conclusions:

• Normal pregnancy is characterized by physiologic absorptive hypercalciuria.
• The findings question the necessity of routine calcium supplementation in well-nourished pregnant women.