Vitamin D metabolism in normal and hypoparathyroid pregnancy and lactation

Abstract

Summary. Plasma concentrations of vitamin D metabolites in −17 non‐pregnant women, 22 pregnant women at delivery, and in eight lactating women 3 and 16 days after delivery, were compared with those in a postpartum hypoparathyroid patient treated with 1α‐hydroxyvitamin D (1α‐OHD). The mean concentration of 1,25‐dihydroxy vitamin D [1,25–(OH)2D] was 203 (SD 61) pmol/1 in the pregnant, and 86 (SD 27) pmol/1 in the non‐pregnant women (P<0.0005). The levels 3. and 16 days after delivery were similar [57 (11) compared with 62 (19) pmol/1], and lower than the non‐pregnant value (P<0.01). The 25‐hydroxyvitamin D (25‐OHD) concentration remained unchanged between the 3rd and 16th days after delivery, whereas the 24,25‐dihydroxyvitamin D [24,25‐(OH)2D] level increased from 2.7 (SD 1.8) to 3.7 (SD 2.3)nmol/l (P<0.025). The patient temporarily required an increased supplement of 1α‐OHD during pregnancy, but a dose which was appropriate before pregnancy resulted in marked hypercalcaemia and a rise of 1,25‐(OH)2D concentration within 16 days of delivery despite lactation. The results suggest that the metabolic need for the active vitamin D metabolite 1,25‐(OH)2D is increased during pregnancy and rapidly reduced during early lactation in healthy and hypoparathyroid women.

Maternal Mineral and Bone Metabolism During Pregnancy, Lactation, and Post-Weaning Recovery

“…In contrast to these reports of improved or stable calcium metabolism, other reports have found that hypoparathyroidism significantly worsens during pregnancy: serum calcium falls, hypocalcemic symptoms may or may not increase, and the doses of supplemental calcium and vitamin D, 1␣-hydroxyvitamin D, or calcitriol have been increased (96,141,148,411,434,510,517,600,669,790,796,821,837,884,936). In one woman the endogenous calcitriol level was low at mid-pregnancy, but measurements in the third trimester were not reported (510).…”

“…Calcium intake is likely an im-portant factor, as it is in the rodent models, with the ideal minimum intake considered to be 1.2 g daily based on the Institute of Medicine guidelines (774). In half of the reports in which hypoparathyroidism appeared to worsen during pregnancy, either no supplemental calcium or at most 300 mg daily was being taken, and the dietary intake of calcium was unknown (96,411,434,510,600,669,790,936). Lack of adequate intake of calcium in the first half of pregnancy likely prevents the net positive calcium balance being achieved that most women experience during pregnancy, and increases the likelihood of problems in the third trimester.…”

European Society of Endocrinology Clinical Guideline: Treatment of chronic hypoparathyroidism in adults

“…These events mandate careful monitoring of serum calcium levels in women with HypoPT who are nursing because hypercalcaemia is commonly encountered if vitamin D analogue therapy is not quickly adjusted. The onset of hypercalcaemia during breastfeeding can be immediate (97,101,102,103,104,105) and has even been reported when treating women with HypoPT with longer-acting ergocalciferol, who did not breastfeed (106). Gradually after weaning, the above changes in maternal hormones regress, and a new steady-state is achieved.…”

Management of hypoparathyroidism in pregnancy and lactation — A report of 10 cases

“…Reports thus far have demonstrated that whilst some women have reduced symptoms and decreased calcium and calcitriol requirement during pregnancy, others require increased doses. However, the physiological decline in serum calcium due to haemodilution in pregnancy has sometimes been misinterpreted as worsening hypocalcaemia resulting in the treatment of women based on their laboratory results rather than clinical symptoms (Kovacs, 2011, Eastell et al, 1985, Krysiak et al, 2011, Markestad et al, 1983, Caplan and Beguin, 1990, Rude et al, 1984, Mather et al, 1999, Sadeghi-Nejad et al, 1980, Wright et al, 1969). There is consistent evidence that calcitriol requirements decrease during lactation.…”