A Case of Familial Hypocalciuric Hypercalcemia Coexisting with Hypothyroidism / 대한내과학회지

ABSTRACT

Familial hypocalciuric hypercalcemia (FHH) is a genetic disorder characterized by mild asymptomatic hypercalcemia, hypocalciuria, a decreased urinary calcium-creatinine ratio, and normal or elevated parathyroid hormone levels. FHH is caused by an inactivating heterozygous mutation of the calcium-sensing receptor (CaSR) gene. A 62-year-old woman was referred to our center because of inadequate glucose control. Her son had hypercalcemia. Biochemical and endocrine studies showed hypercalcemia, hypocalciuria, a decreased urinary calcium-creatinine ratio, normal parathyroid hormone levels, normal PTH-related peptide levels, decreased free T4, increased TSH, and thyroid antibody positivity. Direct sequencing analyses revealed a heterozygous mutation of G21R at exon 2 and a single nucleotide polymorphism of R990G at exon 7 of the CaSR gene. Here, we report a case of FHH associated with a heterozygous mutation and a single nucleotide polymorphism of the CaSR gene, which coexisted with autoimmune thyroiditis and hypothyroidism. To our knowledge, this is the first such case reported.