A case of pseudohypoparathyroidism (PHP) type II associated with Bartter's syndrome--restoration of phosphaturic response to parathyroid hormone (PTH) by treatment for hypopotassemia

Abstract

We report a case of PHP Type II whose phosphaturic response to PTH was restored by treatment for complicated Bartter's syndrome. A 34-year-old woman was admitted to our hospital in July 1990 because of tetanic convulsion. The physical examination showed normal blood pressure (118/62mmHg), round face without shortness of metacarpal bones and positive Trousseau's sign. Although renal function was normal, hypocalcemia (6.5mg/dl) and hyperphosphatemia (4.8mg/dl) in association with high levels of serum PTH (942pg/ml) and 1.25 (OH)2D3 (86pg/ml) were disclosed. Ellsworth-Howard test revealed that there was no increase in the urinary secretion of phosphate despite an increase in urinary cAMP excretion. On the other hand, hypopotassemia (2.5mEq/l) and metabolic alkalosis with high plasma renin activity (22.8ng/ml/hr) and aldosterone concentration (22.7ng/dl) were coexistent. Pressor response to angiotensin II infusion was blunted. Although no glomeruli were obtained by renal biopsy specimen, vacuolar degeneration on proximal tubules were noted. These findings indicated that she had PHP Type II associated with Bartter's syndrome. By administration of potassium (24mEq/day), spironolactone (50mg/day) and only small doses of 1 alpha-hydroxyvitamin D3 (0.5mg/day), serum levels of potassium as well as calcium were normalized and tetanic attacks disappeared. In March 1991, she was re-examined by Ellsworth-Howard test in order to clarify the effects of hypopotassemia on renal tubular response to PTH. Interestingly, phosphaturic response to PTH was restored, and the degree of increase in urinary cAMP excretion was 4 times as high as that on the first admission. These results suggest that hypopotassemia changes the response of renal proximal tubular cells to PTH, particularly such as reabsorption of phosphate and cAMP response, although it is possible that hypocalcemia may contribute to the blunted phosphaturic response to PTH. The mechanism of hypocalcemia seen in this case remains to be elucidated.