899 HYPOPARATHYROIDISM (hPTH) ASSOCIATED WITH NEPHROGENIC DIABETES INSIPIDUS & INCOMPLETE RENAL TUBULAR ACIDOSIS

Abstract

A male infant of healthy parents (birth weight 3374 gm) developed tetany at 6 days of age. hPTH was diagnosed based on hypercalcemia (6.9 mg/dl), hyperphosphatemia (9.0 mg/dl), hypercalcemic and phosphaturic response to paratharmone with clinical and biochemical response to vitamin D (25000 units). Hyposthenuria was noted at 6 mos. The child was reevaluated at 12 yrs of age for polyuria unaffected by water restriction. Creatinine clearance, ACTH stimulation test, skeletal x-rays and IVP were normal but nephrocalcinosis was noted. Water deprivation (20 hrs) resulted in 4.4% weight loss, fixed low urine osmolality (Osm) and fixed urine flow. The final urine Osm was 379 mOsm/kg, urine flow 55 ml/hr, and serum Osm 287 mOsm/kg. One and two hours after 5 units of aqueous vasopressin (VP) injection the urine osmolality remained 378 and 377 mOsm/kg. Lowest urine pH during 5 hr NH₄C1 test was 5.95. Three day NH₄C1 test: baseline titrable acidity (TA) was 12.9 mEq/1, serum CO₂ 24 mEq/1, serum C1⁻ 103 mEq/1. Values after NH₄C1 ingestion were 21.5, 18, & 112, respectively. Normally, in urine there is a rise of ≥ 36 mEq/TA per 24 hrs. The absence of renal response to VP and impairment of urine acidification on acid load may be a vitamin D effect. The presence of hyposthenuria in early infancy with later development of nephrocalcinosis suggest a true association with hPTH; previously unreported.

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