Hypocalcemic Tetany Transiently "Cured" by Pregnancy: A Case Report

Hypocalcemia is an uncommon electrolyte abnormality. We evaluated a young woman with episodes of recurrent symptomatic hypocalcemia, which had started in her late teens. She was hypertensive and laboratory evaluation revealed elevated parathyroid hormone, elevated phosphate, and decreased renal phosphate excretion along with low ionized calcium levels. Her renin and aldosterone levels were elevated. While the response to treatment with calcium and 1,25(OH)₂ dihydroxyvitamin D was modest, her laboratory values and symptoms improved significantly during pregnancy and then recurred post-delivery. Based on clinical and laboratory features, we made a diagnosis of pseudohypoparathyroidism type Ib (PHP1B). Her genomic DNA revealed broad methylation changes at the GNAS locus, which encodes the α-subunit of the stimulatory G protein (Gα_s), without evidence for a deletion or duplication, consistent with PHP1B. Analyses of several microsatellite markers on chromosome 20 performed on our patient and her parents provided no evidence for paternal uniparental isodisomy/heterodisomy of chromosome 20q13.3 (patUPD20q). The approach to hypocalcemia; classification, clinical features, and genetic/epigenetic basis for pseudohypoparathyroidism; alterations of mineral metabolism in PHP1B and pregnancy; and implications for the high renin and aldosterone levels and hypokalemia are discussed.