Primary hyperparathyroidism: Labs to order, Tx to consider

Perform imaging before surgery to identify the overactive parathyroid glands. Ultrasound can detect enlargement of the parathyroid glands. A sestamibi scan, which measures the uptake of Tc99-sestamibi by the parathyroid glands, reflects the activity of the parathyroid glands. In cases of nonlocalization by these 2 modalities, other imaging techniques like 4D CT scan and contrast-enhanced ultrasound can be used. Of note: Imaging is used for localization, but not for diagnosis.

A 24-hour urinary Ca²⁺ excretion is used to assess the risk of renal stones and to differentiate primary hyperparathyroidism from familial hypocalciuric hypercalcemia.

Intra-operative PTH measurement has added to the efficacy of minimally invasive parathyroidectomy. A drop in PTH of >50% after 10 to 15 minutes of excising the gland is considered to be positive.¹⁰

Medication management

Monitor patients who refuse surgery or those who do not meet the criteria after surgery. Serum Ca²⁺ and PTH are monitored annually. DEXA scan needs to be repeated every 1 to 2 years based on the clinical picture. Also assess patients for any fragility fractures and renal endpoints. Recommend taking vitamin D to keep the level above 20 ng/dL.¹⁰ Ca²⁺ intake should follow normally recommended guidelines.

Bisphosphonates are primarily used for the treatment of osteoporosis accompanying PHPT. They decrease bone resorption and, to a lesser extent, bone formation. Alendronate increases BMD at the lumbar spine, but does not have much effect on Ca²⁺ and PTH levels.

Calcimimetics act by mimicking the effects of Ca²⁺ on the Ca²⁺ receptors present on the surface of the parathyroid cells. Therefore, calcimimetics reduce the level of parathyroid hormone and Ca²⁺ levels. (Long-term benefits have not been established.) Bisphosphonates are prescribed for osteoporosis and calcimimetics for hypercalcemia.¹⁰

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