Parathyroid Adenoma
A parathyroid adenoma is a benign tumor of one of the parathyroid glands, four small glands located behind the thyroid that help regulate calcium balance in the body. A single adenoma is the most common cause of primary hyperparathyroidism, a condition in which the parathyroid glands produce excess parathyroid hormone (PTH), leading to elevated blood calcium. Many patients are identified through routine blood tests showing high calcium, while others develop symptoms related to hypercalcemia or its long-term effects on bones, kidneys, and other organs. Evaluation typically combines biochemical testing with parathyroid ultrasound and, when surgery is planned, one or more localization studies such as sestamibi scanning, 4D CT, or MRI.
What is it?
The parathyroid glands are four small glands, each usually about the size of a grain of rice, located behind the thyroid gland in the neck.
They produce parathyroid hormone (PTH), which plays a central role in regulating calcium in the body. PTH raises blood calcium by acting on the bones, releasing stored calcium; on the kidneys, increasing calcium reabsorption and activating vitamin D; and, indirectly through vitamin D, on the intestines, increasing absorption of calcium from food.
This tightly regulated system keeps calcium levels within a narrow range, which is essential for nerve function, muscle activity, bone health, and many other body processes.
A parathyroid adenoma is a benign tumor arising from one of the parathyroid glands. It typically produces PTH autonomously, meaning production continues without the normal feedback control from blood calcium.
Sustained overproduction of PTH raises blood calcium and causes primary hyperparathyroidism.
A single parathyroid adenoma is by far the most common cause of primary hyperparathyroidism. Less common causes include hyperplasia of multiple parathyroid glands and, rarely, parathyroid carcinoma.
Multi-gland hyperplasia is more common in hereditary syndromes, but it may also occur without a known hereditary cause.
Parathyroid carcinoma is rare and often presents with markedly elevated calcium and PTH, a palpable neck mass, or unusually severe symptoms. Distinguishing it from a benign adenoma is not usually straightforward with imaging alone.
Most parathyroid adenomas occur sporadically without an identified underlying cause.
Recognized risk factors include prior radiation to the head or neck, particularly during childhood or adolescence, and long-term use of lithium.
Hereditary syndromes account for a smaller but important proportion of cases. Examples include multiple endocrine neoplasia type 1 (MEN 1), MEN 2A, MEN 4, familial isolated hyperparathyroidism, and hyperparathyroidism-jaw tumor syndrome, which is associated with CDC73 (HRPT2) mutations and an increased risk of parathyroid carcinoma.
Younger age at diagnosis, multiple affected glands, unusually high PTH, marked hypercalcemia, or a personal or family history of related tumors should raise consideration of a hereditary cause.
Primary hyperparathyroidism from a parathyroid adenoma is often identified through routine blood tests showing elevated calcium, sometimes years before any symptoms develop.
Modern presentations are frequently mild or asymptomatic, but the condition can still affect bone, kidney, cardiovascular, and cognitive health over time.
Classic symptoms of hypercalcemia are sometimes summarized as “bones, stones, groans, and psychiatric moans,” referring to bone pain and fragility, kidney stones, gastrointestinal complaints, and mood or cognitive symptoms.
In practice, many patients have vague, nonspecific symptoms such as fatigue, weakness, mild cognitive changes, low mood, poor sleep, or reduced quality of life. These features can be difficult to attribute to hyperparathyroidism with certainty.
Other patients experience kidney stones, calcium in the urine above expected levels, frequent urination, increased thirst, bone or joint pain, constipation, nausea, or high blood pressure. Severe hypercalcemia can cause confusion, marked muscle weakness, or heart-rhythm changes.
Long-term effects of untreated primary hyperparathyroidism may include reduced bone density and increased fracture risk, kidney stones, and reduced kidney function. Cardiovascular effects have also been reported, although the extent varies among patients and is not fully established.
Severe hypercalcemia can, uncommonly, cause a hypercalcemic crisis, which is a medical emergency.
Diagnosis of primary hyperparathyroidism begins with laboratory testing.
Total calcium is measured first, and ionized calcium may be measured when it would clarify a borderline or discordant result. Albumin, kidney function, phosphorus, PTH, and 25-hydroxyvitamin D are also assessed.
The classic biochemical picture is elevated calcium with a PTH level that is elevated or, importantly, inappropriately high-normal for the level of calcium.
Vitamin D status must be considered because low 25-hydroxyvitamin D can raise PTH and complicate interpretation.
A 24-hour urinary calcium measurement is generally recommended before parathyroid surgery. It helps distinguish primary hyperparathyroidism from familial hypocalciuric hypercalcemia (FHH), a benign inherited condition that mimics primary hyperparathyroidism biochemically but does not benefit from surgery.
The calcium-to-creatinine clearance ratio is often used to support this distinction. In selected cases, genetic testing for calcium-sensing receptor or related mutations is appropriate.
Bone density testing (DEXA) evaluates bone health at the lumbar spine, hip, and distal one-third radius. Evaluation of the distal one-third radius is important because primary hyperparathyroidism can affect cortical bone earlier and more prominently than other sites.
Imaging for vertebral fractures or kidney stones may be used depending on the clinical situation.
Once primary hyperparathyroidism is confirmed biochemically and surgery is being considered, imaging is used to try to localize the abnormal parathyroid gland or glands. Imaging supports minimally invasive surgical planning but is not used to establish the diagnosis of hyperparathyroidism.
A negative or inconclusive imaging result does not rule out primary hyperparathyroidism. If the biochemical diagnosis is confirmed and surgery is appropriate, an experienced parathyroid surgeon can proceed with bilateral neck exploration.
Ultrasound of the neck, performed by an experienced operator, can identify many parathyroid adenomas as characteristic hypoechoic lesions near the thyroid. It is limited for retrosternal, deep, or ectopic lesions.
Sestamibi (Tc-99m sestamibi) scanning, often combined with SPECT or SPECT/CT, uses a radiotracer that is preferentially retained by hyperfunctioning parathyroid tissue.
4D CT (parathyroid CT) provides detailed anatomical and dynamic contrast information about the parathyroid glands and can be particularly useful when other imaging is inconclusive, in reoperative cases, or for locating ectopic parathyroid tissue.
MRI is sometimes used in specific circumstances, including patients requiring radiation avoidance or those with anatomy that is difficult to characterize by other modalities.
Combining imaging modalities is common, and the choice depends on local expertise and clinical circumstances. No single test is required or preferred for every patient.
Additional preoperative evaluation, including genetic testing and screening for associated tumors, is appropriate when a hereditary syndrome is suspected.
Important to Know
Management of parathyroid adenoma and primary hyperparathyroidism depends on symptoms, calcium and PTH levels, imaging findings, complications, age, other medical conditions, and patient preferences.
Care is best coordinated by primary care clinicians, endocrinologists, and endocrine or head-and-neck surgeons, with input from radiologists, nuclear medicine specialists, geneticists, nephrologists, and other specialists as needed.
Parathyroidectomy — surgical removal of the abnormal parathyroid gland or glands — is the definitive treatment for primary hyperparathyroidism and offers the possibility of cure.
Modern guidelines support parathyroidectomy in all patients with symptomatic disease.
Surgery is also recommended for many asymptomatic patients who meet accepted criteria. These criteria may include age younger than 50 years; serum calcium substantially above the upper limit of normal (approximately 1 mg/dL above the reference range); reduced kidney function (typically eGFR below approximately 60 mL/min/1.73 m²); 24-hour urinary calcium above a defined threshold (typically greater than 400 mg/day) with an assessed increased kidney-stone risk; kidney stones or nephrocalcinosis on imaging; or evidence of reduced bone density, including a T-score of −2.5 or lower at the lumbar spine, femoral neck, total hip, or distal one-third radius, or the presence of a vertebral fracture on imaging.
Additional individualized factors, such as patient preferences, life expectancy, medical comorbidities, and access to reliable long-term monitoring, are also considered.
Preoperative localization studies help identify the abnormal parathyroid gland or glands and support minimally invasive surgical planning.
When a single adenoma is confidently localized, focused parathyroidectomy — targeted removal of the affected gland — is commonly performed. Intraoperative PTH monitoring, in which PTH is measured before and after removal, helps confirm that the abnormal gland has been removed.
Bilateral neck exploration remains appropriate when localization is unclear, when multi-gland disease is suspected (especially in hereditary syndromes), when reoperation is required, or based on surgeon preference and experience.
Success rates and complication rates depend heavily on surgeon experience, and referral to a high-volume parathyroid surgeon is generally recommended for both initial and reoperative cases.
Potential complications include bleeding, neck infection, transient or permanent hypoparathyroidism (which can cause low calcium and symptoms such as tingling, muscle cramping, or spasms), and recurrent laryngeal nerve injury with hoarseness or voice change. Complication rates are typically low in experienced hands.
Postoperative care includes monitoring calcium and PTH levels, watching for hypocalcemia, and providing calcium and vitamin D as needed.
Patients with significant preoperative bone disease or long-standing severe hypercalcemia may develop “hungry bone syndrome,” in which calcium is rapidly deposited into bones after surgery, causing prolonged low calcium and phosphorus. This can require several days or occasionally weeks of intravenous or oral calcium and active-vitamin-D therapy.
Long-term postoperative follow-up focuses on confirming cure, monitoring for recurrent or persistent disease, and assessing bone and kidney health over time.
Medical monitoring is appropriate for patients who do not meet surgical criteria and prefer nonsurgical management.
Monitoring typically includes periodic assessment of calcium, PTH, kidney function, and, based on clinical circumstances, urinary calcium, bone density, and imaging for kidney stones. The frequency of testing is individualized.
Vitamin D deficiency should be corrected to levels considered adequate for bone and mineral health, with the specific target individualized. Rapid correction with high-dose vitamin D can occasionally worsen hypercalcemia and is generally avoided.
Calcium intake at normally recommended levels — rather than a low-calcium diet — is generally encouraged. Chronic calcium restriction can worsen bone loss and stimulate PTH.
Adequate hydration is important. Thiazide diuretics and lithium can raise calcium and PTH and may need to be reviewed if they are not clinically essential.
Regular physical activity, particularly weight-bearing and resistance exercise, supports bone health.
Medications play a limited but important role in specific situations.
Cinacalcet, a calcimimetic that acts on the parathyroid gland to lower PTH secretion and reduce calcium, may be used in patients with symptomatic hypercalcemia who are not surgical candidates or whose surgery has not been curative. It is also used in parathyroid carcinoma.
Bisphosphonates or other bone-directed medications may be used to protect bone health in selected patients, particularly those with osteoporosis, elevated fracture risk, or bone loss that persists after surgery.
Patients with hereditary syndromes such as MEN 1, MEN 2A, or MEN 4 often benefit from care that accounts for likely multi-gland involvement, higher recurrence risk, coordinated screening for associated endocrine tumors, and family evaluation.
Genetic counseling is important in these situations. Surgical strategy in multi-gland disease commonly differs from that used for a single adenoma and may include subtotal parathyroidectomy or total parathyroidectomy with autotransplantation.
Patients with suspected or confirmed parathyroid carcinoma require more extensive surgery, often including en bloc removal of the affected parathyroid gland with adjacent tissues when necessary. Long-term monitoring for recurrence and management of persistent or recurrent hypercalcemia are important. Care is best delivered in centers with expertise in this rare disease.
Severe or symptomatic hypercalcemia requires urgent medical treatment, often in a hospital.
Initial treatment typically includes intravenous saline hydration and, when appropriate, medications to lower calcium. These may include intravenous bisphosphonates (such as zoledronic acid), calcitonin for rapid short-term lowering, and, in selected cases, cinacalcet or denosumab.
The choice of therapy depends on the severity of hypercalcemia, kidney function, cardiovascular status, prior treatments, and other clinical factors.
Care is typically coordinated by primary care clinicians, endocrinologists, and endocrine or head-and-neck surgeons, with input from other specialists as needed.
Imaging and laboratory findings should always be interpreted alongside the patient’s symptoms, examination, family history, medications, and broader clinical context, rather than in isolation.
Patient education is an important part of care. Understanding the diagnosis, the reasons for recommended monitoring or surgery, the meaning of laboratory and imaging results, medication use, and warning signs of severe hypercalcemia or postoperative low calcium can all support better outcomes.
Red-flag symptoms include severe muscle weakness, marked confusion or drowsiness, unresponsiveness, extreme thirst and frequent urination, severe abdominal pain, severe nausea and vomiting, severe constipation, irregular heartbeat with dizziness or fainting, marked dehydration, severe muscle cramps or spasms after neck surgery (which may indicate significantly low calcium), fever with a painful or red neck (which may suggest infection), rapid clinical deterioration, or any sudden severe symptoms.
These warrant prompt or urgent medical evaluation, as they may indicate severe hypercalcemia, hypercalcemic crisis, postoperative hypocalcemia, infection, or another serious complication.