Cyclical etidronate and calcium carbonate (with citrate) supplementation for osteoporosis unmasking primary hyperparathyroidism.

An 88 year old lady undergoing cyclical etidronate and calcium carbonate (with citrate) therapy for vertebral osteoporosis was found to be symptomatically hypercalcaemic at the end of the first cycle of treatment. She had been previously asymptomatic and normocalcaemic, but was subsequently found to have primary hyperparathyroidism. This condition is most prevalent in postmenopausal females--the same patient group at risk of osteoporosis. Serum calcium should be measured after commencing cyclical etidronate and calcium carbonate. If hypercalcaemia is detected primary hyperparathyroidism should be excluded as an underlying, cause.