Clinical Scenario:
A 3-week-old infant presents with recurrent generalized seizures. Investigations show:
- Serum calcium: 1.45 mmol/L
- Serum phosphate: 2.5 mmol/L
- Magnesium: normal
- 25-hydroxyvitamin D: normal
- Renal function: normal
- PTH: very low
The infant is initially treated with intravenous calcium gluconate, with temporary improvement. However, the hypocalcemia recurs when calcium supplementation is reduced.
What is the most appropriate long-term treatment?
A. Calcitriol with oral calcium
B. Cholecalciferol alone
C. Magnesium with oral calcium
D. Phosphate restriction alone
E. Thiazide diuretic alone
Correct answer & Explanation:
Explanation
Correct answer: A. Calcitriol with oral calcium
The combination of persistent hypocalcemia, marked hyperphosphatemia, normal magnesium and vitamin D, and a very low PTH level indicates impaired parathyroid hormone activity.
The initial seizures and severe hypocalcemia require IV calcium gluconate for acute stabilization. However, because the underlying problem is persistent PTH deficiency, calcium alone will not provide adequate long-term control.
Long-term management consists of oral calcium supplementation together with active vitamin D (calcitriol). Calcitriol increases intestinal calcium absorption and helps maintain serum calcium despite the lack of adequate PTH activity.
Treatment should be monitored carefully with serum calcium, phosphate, renal function and urinary calcium, because excessive calcium/calcitriol therapy can cause hypercalciuria and nephrocalcinosis.
Exam pearl:
Hypoparathyroidism → acute symptomatic hypocalcemia: IV calcium; long-term treatment: oral calcium + active vitamin D (calcitriol).
References
- Brandi ML, et al. Management of hypoparathyroidism: present and future. Journal of Clinical Endocrinology & Metabolism.
- Bilezikian JP, et al. Evaluation and Management of Hypoparathyroidism: Summary Statement and Guidelines. Journal of Clinical Endocrinology & Metabolism.
- Pediatric Endocrine Society. Hypocalcemia in Children and Adolescents.
