A 20-year-old female is referred to your office by her pediatrician. The patient has been followed by her pediatrician for idiopathic hypoparathyroidism for the past four years. She takes vitamin D 50,000 units with 1.5 g of elemental calcium every day. She denies any symptoms. The physical examination is unremarkable, including a negative Chvostek's sign. Her calcium level is 7.8 mg/dL, and phosphorus level is of 5.2 mg/dL. Her 24-hour urinary calcium is 680 mg. What is the next best step in the management of this patient?

Question

A 20-year-old female is referred to your office by her pediatrician.  The patient has been followed by her pediatrician for idiopathic hypoparathyroidism for the past four years.  She takes vitamin D 50,000 units with 1.5 g of elemental calcium every day.  She denies any symptoms.  The physical examination is unremarkable, including a negative Chvostek's sign.  Her calcium level is 7.8 mg/dL, and phosphorus level is of 5.2 mg/dL.  Her 24-hour urinary calcium is 680 mg.  What is the next best step in the management of this patient?

Quizplus · Accepted Answer

Explanation: Patients with hypoparathyroidism are treated with vitamin D (Calciferol), or its active form, 1,25-dihydroxyvitamin D (calcitriol). Patients with chronic hypoparathyroidism are usually managed by giving them high doses of vitamin D and calcium. Vitamin D is generally preferred over 1,25-dihydroxy vitamin D for chronic management in most patients because it is cheaper and effective. The usual dose of vitamin D varies from 25,000 units to 100,000 units per day. High doses of vitamin D are required in hypoparathyroid patients because of the defective conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D in the kidneys resulting from low PTH levels. The dose of vitamin D and calcium is adjusted to keep the calcium levels between 8.5 and 9 mg/dL. After starting treatment with vitamin D and calcium, majority of the patients will have an increase in their urinary calcium excretion due to low PTH levels (PTH increases renal calcium reabsorption). In patients with borderline low serum calcium and high urinary calcium, as seen in the patient described in the vignette, the addition of a thiazide diuretic will not only decrease the urinary calcium, but also increase serum calcium levels. The addition of a thiazide diuretic is therefore the next best step in the management of this patient. (Choice E) If calcium supplementation is increased in this patient, serum calcium is likely to improve; however, her urinary calcium excretion will also increase. Further increasing the urinary calcium excretion will predispose this patient to nephrocalcinosis, renal stones and renal impairment. (Choice B)Decreasing calcium supplementation will worsen this patient's hypocalcemia. (Choice A)In most patients with hypoparathyroidism, hypocalcemia and hyperphosphatemia can be effectively controlled using vitamin D and calcium supplementation. Calcitriol is used in the primary treatment of few patients. It is very useful in patients who are refractory to vitamin D. Compared to the conventional vitamin, calcitriol has a rapid onset of action that lasts for a shorter time. Due to its rapid onset of effect, it is the preferred drug of choice in the management of acute hypocalcemia during the postoperative period. (Choice D) This patient has a borderline low serum calcium and an elevated 24-hour urinary calcium. Continuing the same treatment is likely to harm this patient. Educational Objective: Understand the long-term management of patients with chronic hypoparathyroidism: in patients with borderline low serum calcium and high urinary calcium, as seen in the patient described in the vignette, the addition of a thiazide diuretic will not only decrease the urinary calcium, but also increase serum calcium levels.

A 20-Year-Old Female Is Referred to Your Office by Her