HYPOPARATHYROIDISM IN PREGNANCY AND LACTATION

BALANCING CALCIUM SWINGS

Abstract

INTRODUCTION/BACKGROUND
Management of hypoparathyroidism includes calcium and activated vitamin D supplementation. The dose often requires adjustment during pregnancy and lactation. The combination of increased calcium requirements and the dynamics of parathyroid hormone-related protein (PTHrP) secretion from placental and breast tissue may shift calcium balance to a variable extent.

CASE
A 32-year-old female with a history of hypoparathyroidism after undergoing total thyroidectomy for micropapillary thyroid cancer was followed up during her pregnancy. Her baseline treatment was calcitriol 1.0 mcg and calcium carbonate 1000 mg twice daily. There was a significant drop in serum calcium levels during early pregnancy that required admissions for correction of symptomatic hypocalcaemia. Her calcitriol dose tripled in the first trimester before being slowly reduced back to baseline in the mid-second trimester and stabilizing afterward. She had an uneventful delivery at 37 weeks and gave birth to a healthy newborn. She stopped taking calcitriol postpartum while fully breastfeeding for 4 months and was completely asymptomatic during that period with a documented calcium level of 2.14 mmol/L. However, within 2 weeks of cessation of breastfeeding, she presented with symptoms of hypocalcaemia and a corrected calcium level of 1.87 mmol/L. Treatment with calcitriol was hence reinstated.

CONCLUSION
PTHrP production by the placenta and lactating breast results in increased endogenous calcitriol levels. This subsequently enhances intestinal calcium absorption to meet heightened physiological calcium demands. However, the balance between these two opposing physiologies varies between individuals. This is a rare case documenting a dramatic decline in the need for calcitriol in a patient with hypoparathyroidism during the postpartum and lactation period, followed by a sudden resurgence in calcitriol requirement occurring immediately upon cessation of breastfeeding.