Endocrine Abstracts

JOINT2588

Autosomal dominant hypocalcemia type 1 (ADH1) is a genetic disorder caused by a heterozygous activating mutation in the calcium-sensing receptor (CASR) gene. This mutation decreases the receptor’s sensitivity to low serum calcium, leading to hypocalcemia and low or inappropriately normal levels of parathyroid hormone (PTH). There are only a few reported cases of pregnancies in individuals with ADH1 likely due to the complex physiological changes that occur during pregnancy. These include placental production of PTH-related protein (PTH-rp), expansion of plasma volume, increased fetal calcium demands, and renal hyperfiltration. These factors can disrupt calcium homeostasis, potentially exacerbating maternal hypocalcemia and increasing the risk of fetal hyperparathyroidism as a result of chronic intrauterine hypocalcemia. In women with ADH1, an additional mechanism of non-PTH-mediated hypercalciuria is present, which can worsen renal dysfunction during pregnancy. Furthermore, there is a risk that the fetus may inherit the condition, further complicating the management of these pregnancies. We present the case of a 39-year-old woman who has been under follow-up at our clinic, since being diagnosed with ADH1 at age 30 due to asymptomatic hypocalcemia. Her initial biochemical profile revealed corrected serum calcium (cCa) of 7.64 mg/dL, PTH 17 ng/l and 24-hour urinary calcium excretion of 138 mg/24h. At her most recent pre-pregnancy follow-up, her cCa level was 8 mg/dL. At 15 weeks of pregnancy, her cCa level was of 7.76 mg/dL, while on a regimen of 250 mg of elemental calcium and no calcitriol. Her treatment was progressively increased, and by week 27, with calcium supplementation of 1000 mg/day and calcitriol at 1.25 mg/day, her cCa had risen to 8.6 mg/dL, PTH was 5.1 ng/l and 24-hour urinary calcium was 250 mg/24h. Therapy was maintained, and at 36 weeks, her cCa reached 9.6 mg/dL, PTH was <4 pg/mL, and 24-hour urinary calcium had increased to 572 mg/24h. A cesarean section was performed at 38 weeks. Five days after birth, the neonate exhibited normal calcium levels of 10.1 mg/dL. One month postpartum, during lactation and with unchanged therapy, her cCa level was 8.7 mg/dL. This case highlights the importance of continuous monitoring of calcium levels in individuals with ADH1 to prevent both maternal and fetal complications. Although the literature report urinary complications such as pre-eclampsia and eclampsia, no such events occurred in this patient. Ongoing surveillance of calcium levels in both the mother and the infant remains critical during lactation.