Successful treatment of postsurgical hypoparathyroidism by intramuscular injection of vitamin D₃ in a patient associated with malabsorption syndrome due to multiple abdominal surgeries

A 56-year-old patient with postsurgical hypothyroidism and hypoparathyroidism associated with gastrointestinal malabsorption syndrome was prescribed with l-thyroxine and 1α(OH)D₃ at a massive daily dosage of 600 and 39 μg, respectively. Although the patient became nearly euthyroid, she had been hypocalcemic, requiring frequent intravenous injection of calcium gluconate to prevent tetany. Because the serum level of 1,25(OH)₂D hardly increased after an oral intake of 21 μg 1α(OH)D₃, vitamin D₃ was administered intramuscularly. After stoss therapy (600,000 IU), the patient has been receiving 300,000 IU vitamin D₃ at intervals of 2–4 months so that she remained slightly hypocalcemic (7–8 mg/dl). At 1.5 years later, serum levels of 25(OH)D and 1,25(OH)₂D were maintained at about 60 ng/ml and 30–50 pg/ml, respectively, and renal function was maintained well. These data suggest that intramuscular injection of 300,000 IU vitamin D₃ at an interval of a few months to maintain a slightly increased serum level of 25(OH)D and a slightly decreased serum level of calcium is a safe and cost-effective treatment in such a parathyroid hormone-deficient hypoparathyroid patient with malabsorption syndrome.