[Secondary hyperparathyroidism in the elderly. Apropos of 200 assays of intact parathormone].

Objectives: To evaluate the frequency of high levels of intact parathormone in an elderly population of hospitalized patients and to determine whether there are any correlations with different factors involved in phosphocalcium metabolism, nutritional status and renal function.
Methods: Intact parathormone was assayed in all patients admitted to a geriatric ward (n = 200). Other laboratory tests included serum phosphorus, calcium, total albumin, prealbumin, ionized calcium, creatinine with calculation of the clearance and in 50 patients radioimmunoassay for 25 hydroxyvitamin D.
Results: Intact parathormone was abnormally high (> 65 pg/ml) in 40 patients. Mean levels increased significantly with age and reached 70.5 pg/ml in patients 90 years of age and over. No correlation was found between intact parathormone and total serum calcium, corrected serum calcium, albumin or prealbumin. Inversely there was a significant correlation with serum phosphorus and creatinine and creatinine clearance. Serum levels of 25 hydroxyvitamin D were abnormally low in 82% of the patients. There was a constant and significant decrease in intact parathormone level 15 days after calcium and calcifediol substitution therapy in 13 patients.
Conclusion: The frequency of hyperparathyroidism increases with age to affect nearly 1 out of 2 subjects over 90. It would be useful to determine a threshold level for elderly subjects with a major risk of bone fracture.