From the FDA Drug Label
The dose was not increased if a patient had any of the following: iPTH ≤ 200 pg/mL, serum calcium < 7.8 mg/dL, or any symptoms of hypocalcemia.
The significance of high intact PTH and normal calcium is not directly addressed in the provided drug label. However, it can be inferred that high intact PTH levels are a concern in patients with secondary hyperparathyroidism, and the goal of treatment with cinacalcet is to reduce iPTH levels to ≤ 250 pg/mL.
- Normal calcium levels are also a consideration, as the dose of cinacalcet should not be increased if serum calcium is < 7.8 mg/dL. The provided information does not allow for a conclusion to be drawn about the specific significance of high intact PTH and normal calcium levels in patients treated with cinacalcet 1.
From the Research
High intact parathyroid hormone (PTH) with normal calcium levels typically indicates secondary hyperparathyroidism, most commonly due to vitamin D deficiency. This condition occurs when the body increases PTH production to maintain normal calcium levels despite underlying issues affecting calcium metabolism. The most appropriate initial management includes checking vitamin D levels and supplementing if deficient, usually with 1,000-2,000 IU of vitamin D3 daily or 50,000 IU weekly for 8-12 weeks for severe deficiency, as suggested by the most recent study 2. Other causes to consider include:
- Chronic kidney disease (check renal function)
- Medications (thiazide diuretics, lithium, bisphosphonates)
- Pseudohypoparathyroidism
- Early primary hyperparathyroidism Additional testing should include:
- Phosphorus
- Magnesium
- 25-hydroxyvitamin D
- Possibly 24-hour urinary calcium This pattern occurs because PTH's primary function is to maintain serum calcium within normal range by increasing bone resorption, enhancing renal calcium reabsorption, and promoting vitamin D activation, which in turn increases intestinal calcium absorption. Treatment should address the underlying cause while monitoring both PTH and calcium levels to ensure normalization of the hormonal imbalance, as supported by the study 3 which found that cinacalcet plus vitamin D can be an effective treatment for secondary hyperparathyroidism. However, the most recent study 2 suggests a conservative approach to surgery in normocalcemic primary hyperparathyroidism, emphasizing the importance of careful diagnosis and consideration of medications that can increase PTH secretion.