Summary

• Results from resistance to the actions of PTH produced by a loss of G-protein-mediated signalling.
• Different types are distinguished by the presence or absence of a characteristic skeletal phenotype, the responsiveness to PTH, the underlying mutations, and the inheritance pattern.
• Manifests clinically with hypocalcaemia, hyperphosphataemia, and elevated PTH levels.
• Some patients have associated endocrinopathies. Hypothyroidism is the most common, but hypogonadism is also seen.
• The mainstay of treatment is the normalisation of calcium and phosphate levels using calcium supplementation, vitamin D, and thiazide diuretics. Associated endocrinopathies, if present, are treated with hormone replacement.
• The underlying signalling defects are incurable. Some patients adapt to PTH resistance and have resolution of hypocalcaemia, but others require lifelong calcium supplementation.