Residency · Residency · General Surgery

Hyperparathyroidism: Diagnosis and Surgical Management

Parathyroid Anatomy and Physiology

There are typically four parathyroid glands, though the number ranges from two to six, each weighing approximately 40-60 mg. The superior glands, derived from the fourth pharyngeal pouch, occupy a more consistent position posterior to the recurrent laryngeal nerve near the cricothyroid junction. The inferior glands, derived from the third pharyngeal pouch, are more variable in position and are typically found near the inferior thyroid pole. Ectopic locations include the thymus (the most common ectopic location for inferior glands), the carotid sheath, a retroesophageal position, an intrathyroidal location (2-5%), and the mediastinum. PTH functions to increase serum calcium through bone resorption, renal calcium reabsorption, renal phosphate excretion, and activation of 1,25-dihydroxyvitamin D synthesis. Normal calcium homeostasis relies on PTH secretion being suppressed by rising serum calcium via the calcium-sensing receptor.

Primary Hyperparathyroidism (PHPT)

Epidemiology

Primary hyperparathyroidism is the most common cause of hypercalcemia in outpatients. Its incidence is 1-3 per 1000 with a female predominance of 3:1 and peak occurrence at age 50-60 years. | Pathology | Frequency | Surgical Approach |

A single adenoma accounts for 80-85% of cases, a double adenoma for 5-10%, four-gland hyperplasia for 10-15%, and parathyroid carcinoma for less than 1%.

Clinical Presentation

The classic mnemonic describes the manifestations as "stones, bones, moans, groans, and psychic overtones." Stones refers to nephrolithiasis and nephrocalcinosis. Bones refers to osteoporosis with cortical bone loss, the rare finding of osteitis fibrosa cystica, and fragility fractures. Moans encompasses depression, cognitive dysfunction, and fatigue. Groans includes constipation, nausea, peptic ulcer disease, and pancreatitis. Psychic overtones describes confusion, lethargy, and coma in cases of severe hypercalcemia. However, most patients today are asymptomatic and are detected incidentally on routine laboratory testing.

Diagnosis

The diagnosis is established by an elevated serum calcium (or ionized calcium) with an inappropriately elevated or non-suppressed intact PTH level. Elevated 24-hour urine calcium distinguishes PHPT from familial hypocalciuric hypercalcemia. Additional laboratory studies include phosphorus (which is typically low), vitamin D (often low, and should be repleted before surgery), creatinine, and alkaline phosphatase.

Familial Hypocalciuric Hypercalcemia (FHH)

FHH is an autosomal dominant condition caused by a calcium-sensing receptor mutation. It is a benign condition that mimics PHPT. A calcium-to-creatinine clearance ratio below 0.01 suggests FHH. Surgery is not indicated for FHH.

Indications for Parathyroidectomy (2022 International Guidelines)

Surgery is indicated for symptomatic disease, including nephrolithiasis, fragility fracture, and symptomatic hypercalcemia. For asymptomatic PHPT, surgery is recommended if any of the following criteria are met: serum calcium more than 1.0 mg/dL above the upper limit of normal, creatinine clearance below 60 mL/min, T-score below -2.5 at any site (spine, hip, or distal radius) or vertebral fracture, nephrolithiasis or nephrocalcinosis on imaging, 24-hour urine calcium exceeding 400 mg/day with increased stone risk, or age below 50 years. Surgery may also be considered based on patient preference, even if formal criteria are not met, when symptoms impair quality of life.

<image>Sestamibi-SPECT/CT scan showing focal uptake in a right inferior parathyroid adenoma with delayed washout compared to the thyroid gland</image>

Preoperative Localization

Imaging Modalities

Sestamibi (99mTc-MIBI) scintigraphy relies on differential washout, as parathyroid adenomas retain the tracer longer than thyroid tissue. SPECT/CT improves anatomic localization. Sensitivity is 70-85% for single adenomas but poor for multigland disease and small adenomas. Neck ultrasound is operator-dependent with a sensitivity of 60-80% and can identify concomitant thyroid pathology, though it cannot detect ectopic or mediastinal glands. Four-dimensional CT is a multi-phase CT with contrast timing that shows differential enhancement and washout. It has higher sensitivity than sestamibi at 85-95%, especially for multigland disease and ectopic glands, and is increasingly used as a first-line or adjunctive study. Choline PET/CT (18F-choline or 11C-choline) is an emerging modality with high sensitivity even for small and ectopic adenomas, and is particularly useful in re-operative settings and when other imaging is negative.

Concordance

When two imaging modalities agree on localization (concordant imaging), a focused or minimally invasive parathyroidectomy is supported. Discordant or negative imaging requires bilateral neck exploration.

Surgical Approaches

Focused (Minimally Invasive) Parathyroidectomy

This is a directed approach to a localized adenoma requiring concordant preoperative imaging. A small 2-3 cm incision is centered over the localized gland. Intraoperative PTH monitoring confirms successful excision using the Miami criterion: a PTH drop of more than 50% from the highest pre-excision value at 10 minutes post-excision confirms removal of all hyperfunctioning tissue, eliminating the need to explore all four glands. Advantages include shorter operative time, less dissection, and a lower complication rate for RLN injury and hypoparathyroidism. The success rate exceeds 95-97%.

Bilateral Neck Exploration (BNE)

Bilateral neck exploration is the traditional approach in which all four glands are visualized and assessed. It is indicated when preoperative imaging is discordant or negative, when multigland disease is suspected (hyperplasia, MEN syndromes, or lithium-associated disease), when there is an inadequate IOPTH decline after removal of the localized gland, and in familial PHPT. All four glands are identified, enlarged glands are removed, and the normal size of remaining glands is confirmed. The success rate exceeds 95%.

Intraoperative Adjuncts

IOPTH monitoring is the gold standard adjunct for the focused approach. Frozen section has limited utility because it cannot reliably distinguish parathyroid adenoma from hyperplasia. A gamma probe can be used after sestamibi injection to localize the adenoma intraoperatively in a radioguided parathyroidectomy. Nerve monitoring is optional and may be used for concomitant thyroidectomy or re-operative surgery.

<image>Focused parathyroidectomy technique showing small cervical incision, dissection to the identified parathyroid adenoma, and intraoperative PTH monitoring confirming successful excision</image>

Multigland Disease

In four-gland hyperplasia where all glands are enlarged, management options include subtotal parathyroidectomy (3.5-gland resection), which leaves a well-vascularized remnant of 50-60 mg of the most normal-appearing gland marked with a clip or non-absorbable suture, or total parathyroidectomy with autotransplantation, in which all four glands are removed and a small portion of the most normal gland is minced and implanted into the forearm (brachioradialis) or sternocleidomastoid. Autografting allows confirmation of function by measuring a PTH gradient from the graft arm, and if recurrence develops, the graft can be excised under local anesthesia. The recurrence or persistence rate for multigland disease is 5-20%, higher than for single adenoma.

Special Situations

MEN Syndromes

MEN1 (the 3 Ps: parathyroid, pituitary, pancreas) is associated with PHPT in more than 95% of patients, with multigland hyperplasia being the rule. Surgery involves subtotal parathyroidectomy or total parathyroidectomy with autotransplantation. The recurrence rate is high at 40-60% at 10 years. Concurrent cervical thymectomy should be performed due to the risk of parathyroid tissue in the thymus and thymic neuroendocrine tumors. MEN2A (medullary thyroid cancer, pheochromocytoma, PHPT) involves PHPT in 20-30% of patients. It is addressed at the time of thyroidectomy for MTC, with removal of only enlarged glands and preservation of normal glands.

Parathyroid Carcinoma

Parathyroid carcinoma is rare (less than 1% of PHPT) and should be suspected when calcium exceeds 14 mg/dL, PTH is more than 3-5 times the upper limit of normal, a palpable neck mass is present, or RLN palsy exists. Intraoperatively, the tumor appears firm, white or gray, and adherent to surrounding structures. Surgery involves en bloc resection with ipsilateral thyroid lobectomy and involved adjacent tissues. Capsular rupture must be avoided as spillage increases recurrence. There is no effective adjuvant therapy, and surgery for recurrence remains the mainstay of treatment.

Normocalcemic PHPT

Normocalcemic PHPT is characterized by elevated PTH with consistently normal calcium levels after excluding vitamin D deficiency. It may represent the earliest form of PHPT. Observation is appropriate in most cases, with surgery reserved for symptomatic patients or those meeting surgical criteria for complications such as nephrolithiasis or osteoporosis.

Re-operative Parathyroidectomy

Re-operative surgery is performed for persistent (within 6 months) or recurrent (after 6 months) PHPT. The diagnosis should be reconfirmed by rechecking calcium and PTH and ruling out FHH. Advanced imaging is essential, including 4D-CT, choline PET/CT, and sestamibi SPECT/CT. The prior operative note and pathology should be reviewed to determine what was found and removed. Venous sampling (selective PTH sampling from jugular or thyroid veins) may aid difficult localization. A focused approach is used if the disease is well-localized; a lateral approach anterior to the sternocleidomastoid avoids prior midline dissection. The complication rate is higher than in primary surgery, and these cases should be performed at experienced centers.

<image>Operative photograph showing a parathyroid adenoma being excised during focused parathyroidectomy with the recurrent laryngeal nerve identified and preserved posteriorly</image>

Secondary and Tertiary Hyperparathyroidism

Secondary Hyperparathyroidism

Secondary hyperparathyroidism is caused by chronic kidney disease, in which phosphate retention, decreased 1,25-vitamin D, and hypocalcemia lead to compensatory PTH elevation. All four glands become hyperplastic. Medical management includes phosphate binders, calcitriol or vitamin D analogues, and calcimimetics such as cinacalcet. Surgical indications include disease refractory to medical management (PTH greater than 800 pg/mL), severe symptoms, calciphylaxis, and intractable pruritus. Surgery consists of subtotal parathyroidectomy or total parathyroidectomy with forearm autotransplantation.

Tertiary Hyperparathyroidism

Tertiary hyperparathyroidism involves autonomous PTH secretion that persists after renal transplantation, with hypercalcemia that fails to resolve more than one year post-transplant. Surgery is subtotal parathyroidectomy as the standard approach, though a focused approach may be considered if a single gland is clearly dominant.

Clinical Pearls

A 24-hour urine calcium and calculation of the calcium-creatinine clearance ratio must always be performed before surgery because FHH is the most important diagnosis to exclude, as surgery will not help. Concordant preoperative imaging is required for a focused approach; if imaging is discordant or negative, bilateral exploration should be performed. IOPTH monitoring is the key intraoperative adjunct, and a 50% decline from the highest pre-excision level confirms cure. Vitamin D should be repleted before surgery (target greater than 30 ng/mL) because low vitamin D can worsen postoperative hungry bone syndrome. Hungry bone syndrome, which manifests as severe postoperative hypocalcemia, occurs after removal of a large adenoma in patients with significant bone disease and requires prolonged calcium and vitamin D supplementation. If the adenoma is not found where imaging predicts, a systematic search of ectopic locations should include the thymus, carotid sheath, retroesophageal area, intrathyroidal tissue, and undescended positions above the superior thyroid pole. In MEN1, concurrent cervical thymectomy should always be performed at the time of parathyroidectomy.

References

• Wilhelm SM, et al. The American Association of Endocrine Surgeons guidelines for definitive management of primary hyperparathyroidism. JAMA Surg. 2016;151(10):959-968.
• Udelsman R, et al. One hundred consecutive minimally invasive parathyroid explorations. Ann Surg. 2000;232(3):331-339.
• Cheung K, et al. Role of 4-dimensional computed tomography in patients with primary hyperparathyroidism. World J Surg. 2012;36(6):1340-1345.
• Bilezikian JP, et al. Guidelines for the management of asymptomatic primary hyperparathyroidism: Summary statement from the Fifth International Workshop. J Clin Endocrinol Metab. 2022;107(10):e3964-e3979.
• Thakker RV, et al. Clinical practice guidelines for multiple endocrine neoplasia type 1 (MEN1). J Clin Endocrinol Metab. 2012;97(9):2990-3011.

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