A patient with primary hyperparathyroidism associated with osteomalacia: markedly increased serum levels of intact PTH and 1,25-dihydroxyvitamin D with normo- and hypercalcemia.

A 65-year-old female patient was admitted with complaining chiefly of lower back pains and arthralgia in the bilateral knee joints of 10-years duration. The serum calcium concentration was normal or only slightly increased, whereas the serum intact PTH and 1,25-dihydroxyvitamin D concentrations were substantially increased. Serum phosphate and 25-hydroxyvitamin D concentrations were decreased. Renal function was normal. Serum alkaline phosphatase activity, the osteocalcin concentration and urinary hydroxyproline excretion were markedly increased. Bone X-ray examination showed severe osteopenia and bone biopsy revealed hyperosteoidosis without tetracycline deposition, consistent with osteomalacia. A parathyroid adenoma was demonstrated by echography and CT-scan. Surgical exploration of the neck revealed a chief cell adenoma behind the right upper pole of the thyroid gland. After parathyroidectomy, all the abnormal biochemical data gradually normalized and the patient has been doing well without any symptoms for the last 13 months. These clinical data suggest that osteomalacia of the patient was probably induced by hypophosphatemia of prolonged duration. When hypercalcemia is not evident in a patient with primary hyperparathyroidism, in whom serum alkaline phosphatase and intact PTH levels are inappropriately increased, osteomalacia should be taken into consideration.