Studies of hypoparathyroidism and pseudohypoparathyroidism.
Twenty eight hypocalcaemic patients were studied, 14 with primary hypoparathyroidism, nine with pseudohypoparathyroidism and two with hypo-hyperparathyroidism, to characterized the essential features of these disorders. Like tetany, which was present in 12 of the patients, epilepsy was a common symptom, occurring in 13, seven of whom had received anticonvulsants for two to eight years before hypocalcaemia was detected. Differentiation between primary and pseudohypoparathyroidism could not be made with certainty on clinical grounds but confident distinction could be made by measurement of endogenous parathyroid hormone concentrations and by testing for renal resistance to exogenous parathyroid hormone. This was achieved by measurement of the plasma and, in some patients, the urinary cyclic AMP response to an intravenous injection of highly purified bovine parathyroid hormone. These investigations were also valuable in the assessment of the other three hypocalcaemic patients in whom a diagnosis of parathyroid dysfunction would otherwise have been made. In 10 of the patients synthetic 1 alpha-hydroxylated forms of vitamin D were used to establish and maintain normocalcaemia, though their use required careful monitoring.