From the Research
Diagnosing pseudohypoparathyroidism requires a combination of clinical evaluation, laboratory testing, and sometimes genetic analysis, with the most recent and highest quality study 1 emphasizing the importance of measuring serum calcium, phosphorus, and parathyroid hormone (PTH) levels as the initial step in diagnosis. The diagnostic process begins with measuring serum calcium, phosphorus, and parathyroid hormone (PTH) levels. The classic biochemical pattern includes hypocalcemia, hyperphosphatemia, and elevated PTH levels, indicating resistance to PTH action.
- Key laboratory findings include:
- Hypocalcemia
- Hyperphosphatemia
- Elevated PTH levels
- Additional tests that may be useful in diagnosis include:
- Urinary cAMP and phosphate excretion after PTH administration (Ellsworth-Howard test)
- 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels Physical examination is crucial to identify features of Albright hereditary osteodystrophy (AHO), which may include:
- Short stature
- Rounded face
- Brachydactyly (especially shortening of the 4th and 5th metacarpals)
- Subcutaneous ossifications
- Cognitive impairment Radiographic studies can confirm brachydactyly and detect soft tissue calcifications.
- Genetic testing for mutations in GNAS, STX16, or NESP55 genes helps classify the specific type of pseudohypoparathyroidism (type 1a, 1b, 1c, or 2) and guide management, as recommended by 2 and 3. Family history assessment is important as some forms follow an autosomal dominant inheritance pattern with maternal imprinting. Early diagnosis is essential to prevent complications of chronic hypocalcemia such as seizures, cataracts, and basal ganglia calcifications, and to improve quality of life, as highlighted in 1.