A condition in which increased levels of parathyroid hormone are found in the blood. Three types are recognized: primary, secondary and tertiary.
In the primary form increased parathyroid hormone secretion occurs as a result of abnormality in one or more of the parathyroid glands, usually owing to the presence of adenoma or carcinoma.
In this form the fundamental biochemical finding is persistent hypercalcaemia. The secondary form is associated with abnormalities of parathyroid gland function induced by a sustained hypocalcaemic stimulus, often resulting from chronic renal failure or malabsorption states. In this variety, renal abnormality is associated with additional soft tissue and skeletal changes, and the entire complex is termed renal osteodystrophy.
Tertiary hyperparathyroidism is found in patients with chronic renal failure or malabsorption and secondary hyperparathyroidism of long duration who develop relatively autonomous parathyroid function and hypercalcaemia. The clinical features of primary and secondary hyperparathyroidism differ in some respects.