ORIGINAL RESEARCH article
Front. Endocrinol.
Sec. Developmental Endocrinology
From hypercalcemia to the diagnosis of pseudohypoparathyroidism type 1b: a case report
Małgorzata Rumińska 1
Maria Krajewska 1
Agata Skórka 2,3
Ewelina Witkowska-Sędek 1
1. Department of Pediatrics and Endocrinology, Medical University of Warsaw, Warsaw, Poland
2. Warszawski Uniwersytet Medyczny I Katedra Pediatrii, Warsaw, Poland
3. Instytut Pomnik-Centrum Zdrowia Dziecka, Warsaw, Poland
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Abstract
Pseudohypoparathyroidism type 1b (PHP-1b) is a rare genetic disorder caused by mutations or epigenetic alterations of the maternal GNAS gene, resulting in isolated renal resistance to parathyroid hormone (PTH) and, in some cases, partial resistance to thyroid-stimulating hormone. Clinical manifestations typically result from hypocalcemia and resemble those seen in hypoparathyroidism, while laboratory tests show elevated serum PTH levels along with hypocalcemia and hyperphosphatemia. We present a case of a girl with an unusual course of PHP: from non-autoimmune hypothyroidism coexisting with hypercalcemia at the age of 1 year to the diagnosis of PHP-1b at the age of 3.5 years, before the onset of symptomatic hypoparathyroidism. In the absence of a clear cause for hypothyroidism, assessment of calcium and phosphate metabolism should be considered. Initial hypercalcemia does not exclude the diagnosis of PHP-1b. Long-term monitoring of calcium and phosphate metabolism parameters may be necessary for a final clinical diagnosis.
Summary
Keywords
case report, Children, Hyperphosphatemia, Hypocalcemia, non-autoimmune hypothyroidism, Parathyroid Hormone, Pseudohypoparathyroidism type 1B
Received
31 December 2025
Accepted
16 February 2026
Copyright
© 2026 Rumińska, Krajewska, Skórka and Witkowska-Sędek. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Maria Krajewska
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