Lab Value


A 48-year-old woman with primary hyperparathyroidism has a T score of less than –1.8 at the left distal radius on her dual-energy x-ray absorptiometry (DEXA) scan but is otherwise asymptomatic.

What is the next step in her management?

The approach to a patient with primary hyperparathyroidism is shown in the image.
In patients with otherwise asymptomatic primary hyperparathyroidism, indications for surgery include:

  1. Age <50 years old
  2. Calcium >1 mg/dL above normal
  3. DEXA scan T-score <–2.5 indicating osteoporosis
  4. Glomerular filtration rate <60 mL/min
  5. Vertebral fractures on imaging (x-ray, CT, MRI)
  6. 24-Hour urinary calcium >400 mg/d
  7. Nephrolithiasis, nephrocalcinosis on imaging (ultrasound, x-ray, CT)

Once the decision for surgical management has been made, localization studies aid in planning surgery. Given that 80–85% of patients have a single adenoma, minimally invasive parathyroidectomy can be performed using intraoperative PTH levels to verify biochemical cure.

A combination of studies gives the best chance of localizing the affected parathyroid. The most commonly used imaging studies are ultrasound, 99mTc-sestamibi scan, and CT. Sestamibi with single photon emission computed tomography (SPECT) can pick up abnormal parathyroid tissue in 80–90% of patients. It is limited in patients with smaller adenomas or in patients with thyroid nodules. Ultrasound is heavily operator and equipment-dependent. When high-resolution equipment is used, sensitivity is 70–90% with a specificity of 90–98%. Ultrasound also has the benefit of giving more detailed anatomic information and being able to evaluate any possible thyroid nodules that may be present. If there is thyroid pathology that requires surgical intervention, it can be addressed concurrently with the parathyroid disease. When sestamibi and ultrasound are concordant, localization improves to 94–99%. Utilization of CT has also increased, especially in the reoperative setting. A four-dimensional CT, consisting of precontrast, postcontrast, and delayed images, is particularly useful in identifying parathyroid adenomas. Reported sensitivity can be up to 88%, with a specificity of 92%.