Hypo-hyperparathyroidism: evidence for a defective parathyroid hormone

Area of Science:

• Endocrinology
• Pediatric Endocrinology
• Metabolic Bone Disease

Background:

• Hypoparathyroidism and hyperparathyroidism can present with complex biochemical and clinical features.
• Distinguishing between different forms of parathyroid dysfunction is crucial for effective management.

Observation:

• A 7-year-old girl presented with seizures and tetany, exhibiting hypocalcemia, hyperphosphatemia, and elevated parathyroid hormone (PTH) levels.
• Roentgenographic findings suggested hyperparathyroidism, with increased alkaline phosphatase and subperiosteal bone resorption.
• Somatic features typical of pseudohypoparathyroidism were absent.

Findings:

• Intramuscular parathyroid extract administration corrected hypocalcemia and hyperphosphatemia.
• Vitamin D therapy normalized serum calcium, phosphorus, and alkaline phosphatase, along with PTH levels and bone abnormalities.
• Ethylenediaminetetraacetic acid infusion increased plasma PTH but not urinary cyclic adenosine monophosphate (AMP) or phosphaturia, unlike parathyroid extract.

Implications:

• The patient's endogenous PTH appears to affect bone resorption but not renal phosphate handling, indicating a defect in PTH action or signaling.
• This case highlights a potential novel form of parathyroid hormone resistance or dysfunction.
• Further research is needed to elucidate the precise molecular mechanisms underlying this defective PTH activity.