Increased urinary phosphate excretion in pseudohypoparathyroidism type II with long-term treatment with phosphodiesterase inhibitor

A 58-year-old woman was diagnosed to have pseudohypoparathyroidism (PHP) ty pe II because of the absence of an Increase of urinary phosphate secretion, despite a marked increase in urinary cAMP excretion on the Ellsworth-Howar d test. We treated the patient with a cyclic-nucleotide phosphodiesterase i nhibitor, theophylline, resulting in increased urinary phosphate and cAMP e xcretions. Dibutyl cAMP administration induced the increase in the urinary phosphate excretion. In this case, the unresponsiveness of the urinary phos phate secretion to cAMP was recovered by a high dose of cAMP or long-term a dministration of a phosphodiesterase inhibitor. These data imply that cAMP responsiveness to renal tubular phosphate reabsorption should be more stric tly elucidated in the patient with PHP type II.