Tertiary hyperparathyroidism in patients with pseudohypoparathyroidism type 1a

Area of Science:

• Genetics
• Endocrinology
• Molecular Biology

Background:

• Pseudohypoparathyroidism type 1a (PHP1a) is a genetic disorder characterized by parathyroid hormone (PTH) resistance and Albright's hereditary osteodystrophy, caused by maternal GNAS gene mutations.
• Patients with PHP1a often require long-term management of hypocalcemia.

Purpose of the Study:

• To report two cases of PHP1a with tertiary hyperparathyroidism (HPT).
• To investigate the GNAS gene mutations associated with PHP1a and tertiary HPT.
• To provide treatment recommendations for PHP1a patients at risk of tertiary HPT.

Main Methods:

• Case study of two unrelated PHP1a patients.
• Molecular analysis of the GNAS gene to identify mutations.
• Clinical evaluation of tertiary HPT development and associated bone disease.

Main Results:

• Two unrelated PHP1a patients developed tertiary HPT during hypocalcemia treatment.
• Case 1 had a known GNAS deletion (c.565_568delGACT) and severe osteoporosis, requiring parathyroidectomy.
• Case 2 had a novel GNAS missense mutation (p.Lys233Glu) and was asymptomatic without bone disease.

Conclusions:

• PHP1a patients are susceptible to developing tertiary HPT.
• Long-term management of hypocalcemia in PHP1a requires careful monitoring of PTH levels.
• Treatment with sufficient calcium and vitamin D, aiming for mid-normal to double the upper limit of normal PTH, is recommended regardless of serum calcium levels.