Urinary phosphate and cyclic adenosine monophosphate response to intravenous administration of synthetic human parathyroid hormone-(1-34) in idiopathic hypoparathyroidism, pseudohypoparathyroidism, pseudopseudohypoparathyroidism and normal subjects

Abstract

The response to exogenous parathyroid hormone (PTH) with urinary excretion of phosphate and cyclic adenosine monophosphate (cAMP) was tested by the use of synthetic human parathyroid hormone (1-34) [hPTH-(1-34)] on 59 patients with hypocalcemia and normal or high serum inorganic phosphorus and normal renal function without a history of parathyroidectomy for differentiation between idiopathic hypoparathyroidism (IHP), pseudohypoparathyroidism (PHP) and related diseases along with 18 normal subjects. A positive phosphaturic response to exogenous PTH was defined as the increment of 2 hours phosphate excretion (delta P) of more than 35 mg. A positive urinary cAMP response to exogenous PTH was defined as the increment by more than 1 mumole per one hour (delta cAMP) and the increase of 1 hour excretion by more than 10 times. Increments of 2 hours urinary phosphate excretion in response to hPTH-(1-34) 100 units were 60.5 +/- 7.7 mg (mean +/- SEM) in 27 patients with IHP, 23.5 +/- 5.9 mg in 21 patients with PHP type I and 24.9 +/- 4.0 mg in 17 normal subjects. Increments of 1 hour urinary cAMP excretion in response to hPTH-(1-34) 100 units were 12.0 +/- 1.5 mumole in 27 patients with IHP, 0.33 +/- 0.10 mumole in patients with PHP type I and 23.6 +/- 5.8 mumole in 15 normal subjects. Ratios of 1 hour urinary cAMP excretion were 97 +/- 10 in 27 patients with IHP, 3.6 +/- 0.5 in 21 patients with PHP type I and 54 +/- 14 in 15 normal subjects. Positive phosphaturic and negative urinary cAMP response was encountered in 3 out of 21 patients with PHP type I in response to hPTH-(1-34). This exaggerated phosphaturic response should be considered as due to the influence of treatment with Ca or vitamin D derivatives.