Differentiation of pseudo- and idiopathic hypoparathyroidism by measuring urinary calcitonin

Calcitonin (CT) levels were determined in urine specimens from normal subjects and patients with pseudohypoparathyroidism type I (PHP), idiopathic hypoparathyroidism (IHP), pseudopseudohypoparathyroidism (PPHP), and surgical hypoparathyroidism (SHP). Urinary CT was measured by RIA after extraction of urine by gel chromatography on a 0.8 X 20-cm column of Bio-Gel P-2. The urinary CT level ranged from 420-1000 pg/mg creatinine (Cr; mean +/- SD, 631 +/- 229) in PHP (n = 6), from 50-270 (131 +/- 92) in IHP (n = 6), and from 35-93 (66 +/- 27) in SHP (n = 6), and was 185 pg/mg Cr in one patient with PPHP. The mean value in PHP was significantly (P less than 0.001) higher, and that in SHP was significantly (P less than 0.05) lower, than those in the age-matched normal subjects. In each patient with PHP and IHP before and after treatment with 1 alpha-hydroxycholecalciferol, urinary CT levels fluctuated between 700-1370 pg/mg Cr in PHP and from 43-195 pg/mg Cr in IHP. Increased urinary excretion of CT in patients with PHP suggests that CT secretion may be enhanced in this disease. The biological role of CT in PHP remains to be clarified.