This occurs in 40-80% of MEN 2a patients. The parathyroid tumours cause the same kind of primary hyperparathyroidism as in MEN 1. Interestingly, more than 50% of these patients have no abnormality in their calcium levels and their parathyroid abnormalities are found during thyroidectomy for medullary thyroid carcinoma.
The tumour produces primary hyperparathyroidism (see Parathyroid section for more detail) where excess parathyroid hormone (PTH) is released, raising blood calcium levels (hypercalcaemia). Unlike sporadic primary hyperparathyroidism where a single tumour (adenoma) in one gland is usually seen, the change in MEN is hyperplasia (excess growth) of all four glands.
The raised blood calcium can cause no symptoms at all or it can produce symptoms such as:
No long-term medical treatment exists for primary hyperparathyroidism meaning surgery is the treatment of choice. Subtotal parathyroidectomy or total parathyroidectomy with autotransplantation of some parathyroid tissue are common operations (discussed in detail in the parathyroid section). However due to the fact all four glands are involved the operation has a lower success rate in MEN than when done on sporadic cases where less tissue is involved. 75% patients with normal calcium after the operation. 10-25% are hypoparathyroid (lowered parathyroid function) resulting in the need for calcium and vitamin D replacements. 50% become hypercalcaemic within 10 years due to any remaining tissue quickly regenerating. This compares with a 95% cure rate with sporadic primary hyperparathyroidism due to single gland disease. The best operation is therefore probably total parathyroidectomy without transplantation, with lifelong vitamin D replacement to restore calcium levels in the absence of parathyroid hormone.
Poor surgical results therefore mean that surgery should be delayed until symptoms become significant.
For much more information on parathyroid tumours and parathyroid physiology please see the relevant parts of the 'Parathyroid Gland' section of this website.