Two Pregnancies in A Known Case of Autosomal Dominant Hypocalcemia Type 1 (ADH1) and Hypoparathyroidism (HypoPT): A Case Report

During pregnancy calcium homeostasis is altered¹. Adjustment may need to be made for the doses of calcium and calcitriol to optimize fetal and maternal outcomes(1). Current recommendations advise maintaining a serum corrected calcium within the low normal reference range^2,3.

Case Description:

A 24y.o with ADH1, p.Phe788Cys mutation of the CaSR gene, confirmed at age 10y.o, treated with elemental calcium, calcitriol, and magnesium. Basal ganglia calcifications were confirmed on imaging.

Discussion:

Pregnancy 1: age 20y.o, required tripling of calcium and calcitriol doses in 2nd trimester compared to baseline in order to maintain eucalcemia. In 3rd trimester, calcium requirements declined to baseline, and calcitriol by 50%. Calcitriol further declined by 55% during lactation. Serum corrected calcium ranged between 1.54-1.7mmol/L (N 2.19-2.57) in 1st and 2nd trimesters as she missed several clinic appointments. She required 3 hospital admissions for IV calcium (received total 290g IV calcium). Serum phosphorus was mildly elevated 1.33-2.11 mmol/L (N 0.74-1.52). Magnesium was slightly low 0.56-0.61 mmol/L (N 0.66-1.07) despite supplements. She delivered at 37 wks, baby’s APGARS was 9 (1min),9 (5min), hypocalcemia was present. Baby (2825g) was admitted to NICU for 2wks. Pregnancy 2: age 24y.o, required doubling of calcitriol in 1st trimester and was admitted to hospital due to hypocalcemia. Calcium requirements increased by 50%, and calcitriol by 20%, by the end of 2nd trimester and required a second admission for IV calcium. She breastfed for 2 months, calcium requirements decreased by 50%, and calcitriol by 60% postpartum. Hyperphosphatemia was present throughout pregnancy (PO4 1.83-2.21 mmol/L). She had a c-section at 34 wks for low BPP score 2/8. Neonate (2540g) was admitted to NICU for hypocalcemia.

Conclusion:

During pregnancy rises in PTHrP and calcitriol are expected to lower calcium and calcitriol requirements, however this is not consistently seen in women with HypoPT. As the fetal skeleton develop, calcium requirement may be higher as seen in this case. Poor compliance to therapy can impact fetal and maternal morbidity. It is essential to closely monitor patients and try to maintain serum calcium in the low normal reference range in pregnancy.

References:

1. Kovacs CS. Maternal Mineral and Bone Metabolism During Pregnancy, Lactation, and Post-Weaning Recovery. Physiol Rev. 2016;96(2):449-547.
2. Khan AA, et al. MANAGEMENT OF ENDOCRINE DISEASE: HypoPT in pregnancy: review and evidence-based recommendations for management. EJE. 2019;180(2):R37-R44.
3. Ali DS, et al. HypoPT in Pregnancy and Lactation: Current Approach to Diagnosis and Management. JCM. 2021;10(7):1378.