Renal-Resistant Hormonoplethoric Hypoparathyroidism with Evidence for a Defective Response to cAMP*

Abstract

A 15.5-yr-old black male is reported with hypocalcemia, hyperphosphatemia, and severe osteitis fibrosa cystica. While hypocalcemic and hyperphosphatemic, the circulating parathyroid hormone (PTH) level and urinary cAMP excretion were increased. An infusion of exogenous PTH produced a normal maximal excretion of urinary cAMP but failed to increase phosphate excretion. Correction of the hypocalcemia by administration of 200,000 U vitamin D daily lowered the endogenous PTH level and basal excretion of cAMP to normal; at that time, infusion of PTH produced both a normal rise in urinary cAMP and a normal phosphaturic response. This pattern of response suggests pseudohypoparathyroidism with a calcium-sensitive defect in renal phosphate transport distal to the PTH receptor adenyl cyclase mechanism, producing hyperphosphatemia, hypocalcemia, and secondary hyperparathyroidism. The osteitis fibrosa cystica was presumably due to the increased PTH, suggesting that resistance to PTH was present in kidney but not bone.

Basal Ganglia Calcification in Pseudohypoparathyroidism Type Ii

“…Among patients with PsHP type 11, some have a combined bone and kidney insensitivity to PTH (Drezner et al, 1976;Rodriguez et al, 1974) whereas the defect is limited to the kidney in others; in these, severe ostitis fibrosa may develop due to preserved sensitivity of bone (Duck et al, 1978). The insensitivity to PTH of the renal tubules appears to be reversible in some patients when hypocalcaemia is corrected either by (Rodriguez et ai., 1974) or by treatment with pharmacological amounts of vitamin D3 (Duck et al, 1978), after which the phosphaturic response to PTH is restored.…”