Delayed diagnosis of pseudohypoparathyroidism type 1a with rare hypothyroidism since childhood

Pseudohypoparathyroidism (PHP) is a rare disorder that associates with resistance to parathyroid hormone (PTH). A 21-year old man visited outpatient clinic to treat previously diagnosed hypothyroidism and vitamin D deficiency. Despite daily 150 mcg of levothyroxine supplement, thyroid-stimulating hormone level was elevated, but thyroid autoantibodies were not detected. He showed features of Albright Hereditary Osteodystrophy and elevated serum PTH level with normal albumin-corrected calcium and phosphorus level. The Ellsworth-Howard test proved the blunted response of urinary phosphorus and cyclic adenosine monophosphate after the infusion of the exogenous PTH, suggesting PTH resistance. DNA analysis revealed a heterozygous mutation in the GNAS gene (c.478C > T). Herein, we report a case of PHP type 1a confirmed by clinical, biochemical and molecular analyses. Establishing correct diagnosis of PHP is necessary for efficient therapeutic management.