In this episode of Hospital Medicine Unplugged, we break down primary hyperparathyroidism (PHPT)—from epidemiology and pathophysiology to modern imaging, surgical indications, and evolving medical therapies.

We start with who gets PHPT and how often it occurs. The condition affects ~0.8–0.9% of the general population, with an incidence of 4–6 cases per 10,000 person-years. It is 2.5 times more common in women, and incidence rises sharply with age, reaching ~12 cases per 10,000 person-years in people aged 70–79. There are also racial disparities, with higher incidence reported in Black populations.

Next we unpack the causes of PHPT. About 80% of cases result from a single parathyroid adenoma, 10–11% from multiple adenomas, <10% from four-gland hyperplasia, and <1% from parathyroid carcinoma. Some cases occur in genetic syndromes such as MEN1, MEN2A, MEN4, and hyperparathyroidism–jaw tumor syndrome.

Clinically, up to 80% of patients in resource-rich settings are now asymptomatic, discovered incidentally through routine lab testing. When symptoms occur, they reflect hypercalcemia and PTH excess, including kidney stones, osteoporosis, gastrointestinal symptoms, and neuromuscular complaints. Many patients also report fatigue, depression, or cognitive symptoms, though the direct causal relationship remains debated.

We then cover complications that drive treatment decisions. PHPT can lead to osteoporosis, fragility fractures, nephrolithiasis, and reduced kidney function. There is also growing evidence linking PHPT with hypertension, left ventricular hypertrophy, and increased cardiovascular risk, though cardiovascular benefit from surgery remains uncertain.

Diagnosis starts with biochemical confirmation—elevated calcium with inappropriately elevated PTH. Imaging is not for diagnosis but for surgical planning. The usual first-line localization strategy combines neck ultrasound with dual-tracer sestamibi scanning, while second-line imaging options such as 4D-CT or 18F-fluorocholine PET/CT offer extremely high sensitivity—up to ~94–99%.

Management centers on parathyroidectomy, which is the definitive treatment. Current guidelines recommend surgery for patients with: • Serum calcium >1 mg/dL above normal • Age <50 years • Osteoporosis (T-score ≤ −2.5) or vertebral fracture • Kidney disease (eGFR <60) • Hypercalciuria (>250 mg/day in women, >300 mg/day in men) • Kidney stones or nephrocalcinosis • Symptomatic disease

For patients who are not surgical candidates, several medications help control complications: • Cinacalcet lowers serum calcium and PTH but does not improve bone density • Bisphosphonates (like alendronate) improve bone density but do not lower calcium • Denosumab and combination therapy with cinacalcet may help address both hypercalcemia and bone loss

We also explore normocalcemic primary hyperparathyroidism, an increasingly recognized condition defined by elevated PTH with normal calcium after excluding secondary causes. It may represent an early or milder form of PHPT, often with more multiglandular disease and slightly lower surgical cure rates.

Finally, we highlight critical diagnostic pitfalls and emerging research. Distinguishing PHPT from familial hypocalciuric hypercalcemia (FHH) is essential—FHH shows lifelong mild hypercalcemia and a calcium-to-creatinine clearance ratio <0.01 and does not require surgery. Meanwhile, advanced imaging, genetic testing in younger patients, and combination pharmacotherapy are shaping the future of PHPT care.

The bottom line: primary hyperparathyroidism is common, increasingly detected incidentally, and highly treatable—especially when clinicians recognize surgical indications, use modern imaging strategies, and tailor therapy to complications and patient risk.