Parathyroid function in Paget's disease of bone.

In order to determine the prevalence of secondary hyperparathyroidism in patients with Paget's disease of bone, we measured serum parathyroid hormone levels (N-terminal assay) in 39 patients with a wide range of pagetic activity. All patients had normal serum calcium levels. A total of 30 patients were either untreated or had received no treatment for 6 months or longer when studied; the other 9 were receiving either salmon calcitonin (3) or EHDP (6). The results showed that in 7 of the 39 patients (18%) parathyroid hormone levels were increased above normal. These were among the most severely affected cases, as manifested by the degree of elevation of three pagetic biochemical indices: serum alkaline phosphatase, plasma bone Gla protein, and 24 h urinary hydroxyproline-creatinine ratios. Levels of 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 were normal. We examined the relationships between parathyroid hormone and each of the three pagetic indices as well as serum calcium for the entire group of 39 patients. Parathyroid hormone values did not correlate with serum calcium measurements (r = -0.241, p = NS) but did correlate significantly with serum alkaline phosphatase (r = 0.496, p less than 0.001), plasma bone Gla protein (r = 0.537, p less than 0.001), and urinary hydroxyproline (r = 0.450, p less than 0.011). We conclude that relative or absolute increases in parathyroid hormone may occur in moderately active Paget's disease, possibly in the setting of greater calcium demands during periods of increased pagetic new bone formation.(ABSTRACT TRUNCATED AT 250 WORDS)