From the Guidelines
Diagnosing parahyperthyroidism primarily involves biochemical testing, specifically measuring serum calcium and parathyroid hormone (PTH) levels simultaneously, as imaging has no role in confirming or excluding the diagnosis. The diagnosis of parahyperthyroidism is made through biochemical testing, which shows hypercalcemia with inappropriately normal or elevated PTH levels 1. Additional laboratory tests include measuring phosphorus, 25-hydroxyvitamin D, and 24-hour urinary calcium excretion, as well as renal function tests to assess for kidney damage.
Key Diagnostic Steps
- Measure serum calcium and PTH levels simultaneously to establish the diagnosis of parahyperthyroidism
- Perform additional laboratory tests, such as phosphorus, 25-hydroxyvitamin D, and 24-hour urinary calcium excretion
- Assess renal function to evaluate for potential kidney damage
- Use imaging studies, like ultrasound of the neck, 99mTc-sestamibi scintigraphy, 4D-CT, or MRI, for localization of the parathyroid adenoma once the biochemical diagnosis is established 1
Importance of Biochemical Testing
Biochemical testing is crucial in diagnosing parahyperthyroidism, as it helps distinguish the condition from other disorders of calcium metabolism. The diagnosis is confirmed when laboratory findings show hypercalcemia with non-suppressed PTH levels in the absence of other causes, such as thiazide diuretic use, lithium therapy, or familial hypocalciuric hypercalcemia.
Role of Imaging
Imaging studies are essential for preoperative parathyroid gland localization, particularly in cases where minimally invasive parathyroidectomy is planned 1. However, imaging has no utility in confirming or excluding the diagnosis of parahyperthyroidism, which is primarily based on biochemical testing 1.
From the Research
Diagnosis of Primary Hyperparathyroidism
To diagnose primary hyperparathyroidism (PHPT), the following steps can be taken:
- Evaluate patients with clinical histories of nephrolithiasis, nephrocalcinosis, osseous pain, subperiosteal resorption, and pathologic fractures, as well as those with osteoporosis-osteopenia, a personal history of neck irradiation, or a family history of multiple endocrine neoplasia syndrome (types 1 or 2) 2.
- Measure parathyroid hormone (PTH) levels, as well as phosphate, chloride, 25-hydroxyvitamin D, 1,25 dihydroxyvitamin D, and calcium-to-creatinine clearance for differential diagnosis 2.
- Identify asymptomatic hypercalcemia without guiding signs or symptoms, which is the most frequent manifestation of the disease 2.
Biochemical Profiles
Patients with PHPT present with distinct biochemical profiles, including:
- Elevated or inappropriately normal serum PTH concentrations in the presence of hypercalcemia or normal-high serum calcium levels 2, 3.
- A near-normal Gaussian distribution of both calcium and PTH levels, with an average calcium concentration of 10.9 ± 0.6 mg/dL and an average PTH concentration of 105.8 ± 48 pg/mL 4.
- Normocalcemic hyperparathyroidism, which is seen in a small percentage of patients 4, 3.
Diagnostic Considerations
When diagnosing PHPT, consider the following:
- The disease can be asymptomatic, but it always has the potential to become symptomatic, resulting in bone loss and kidney stones 3.
- Parathyroidectomy is the only curative treatment for PHPT, and it is recommended in patients with symptoms and those with asymptomatic disease who are at risk of progression or have subclinical evidence of end-organ sequelae 3, 5, 6.
- Medical management may be considered in patients with mild asymptomatic disease, contraindications to surgery, or failed previous surgical intervention 5.