Special Surgery 4. Surgery of the Parathyroid Gland

I. Parathyroid Anatomy and Physiology

Anatomy

• Usually 4 parathyroid glands
• Located behind/posterior to the thyroid gland
• Inferior glands are more variable; ectopic glands may be in thymus/mediastinum or intrathyroidal
• Close relation to recurrent laryngeal nerve → Important surgical risk
• Incision for cervical parathyroid surgery: Kocher collar incision above suprasternal notch

Physiology

• Parathyroid gland secretes PTH
• PTH regulates calcium and phosphate balance
• Low Ca2+ → Increased PTH secretion
• PTH effects:

• Bone → Increased osteoclast activity indirectly → Ca2+ release, decreased bone density
• Kidney → Increased Ca2+ reabsorption, decreased phosphate reabsorption
• Kidney → Increased vitamin D activation → Increased intestinal Ca2+ absorption

• Excess PTH → Hypercalcemia + bone loss
• PTH deficiency → Hypocalcemia

II. Hyperparathyroidism: Types, Clinical Features and Diagnosis

Definition

• Hyperparathyroidism: Excessive PTH production/effect
• Most common in 6th decade; more common in women
• Children/young patients → Consider MEN1/MEN2

Etiologic Classification

1. Primary Hyperparathyroidism

• Autonomous hyperfunction of parathyroid gland(s)
• Most common cause of outpatient hypercalcemia
• Labs → High PTH, high Ca2+, low phosphate
• Causes:

• Single parathyroid adenoma: about 80-85%
• Diffuse/multiglandular hyperplasia
• Double adenoma
• Parathyroid carcinoma: rare, <1%

2. Secondary Hyperparathyroidism

• Physiological compensatory PTH secretion due to hypocalcemic stimulus
• Causes → Chronic renal failure, vitamin D deficiency, malabsorption
• CKD labs → High PTH, low/normal Ca2+, high phosphate
• Vitamin D deficiency labs → High PTH, low/normal Ca2+, low/normal phosphate

3. Tertiary Hyperparathyroidism

• Long-term secondary hyperparathyroidism → Parathyroid hyperplasia → Autonomous PTH secretion
• Does not respond normally to serum Ca2+ feedback
• Often after long-standing CKD or renal transplantation
• Labs → High PTH, high Ca2+, often high phosphate if renal failure persists

Clinical Features

• Classical mnemonic: bones, stones, groans and psychic overtones

• Bones → Bone pain, osteopenia/osteoporosis, fractures, osteitis fibrosa cystica/osteomalacia-like pain
• Stones → Nephrolithiasis, recurrent urinary tract calculi
• Groans → Constipation, nausea, abdominal pain, peptic ulcer, pancreatitis
• Psychic overtones → Fatigue, depression, confusion, mental changes

• Other hypercalcemia signs → Muscle weakness, polyuria, polydipsia, dehydration
• Secondary HPT in CKD → Renal osteodystrophy, pruritus, vascular/soft-tissue calcification, calciphylaxis in severe cases

Diagnosis

1. Biochemical Diagnosis

• Diagnosis is biochemical first; imaging is for localization after diagnosis
• Serum Ca2+ corrected for albumin or ionized Ca2+
• Serum intact PTH
• Serum phosphate, creatinine/eGFR, 25-OH vitamin D
• Urine Ca2+ in primary HPT → Helps distinguish from familial hypocalciuric hypercalcemia (FHH)
• Exclude secondary causes before diagnosing primary HPT

2. Complication Assessment

• Bone mineral density / DXA → Osteoporosis, fracture risk
• Renal imaging → Nephrolithiasis/nephrocalcinosis
• Renal function and stone history

3. Localization Imaging Before Surgery

• Goal → Localize adenoma and plan focused operation
• Ultrasound
• Tc-99m sestamibi scintigraphy / SPECT-CT
• 4D-CT, MRI or PET only in selected difficult/negative/reoperative cases
• Negative imaging does not exclude biochemical hyperparathyroidism

III. Parathyroid Surgery

Indications for Surgery

1. Primary Hyperparathyroidism

• Parathyroidectomy is definitive treatment
• Indicated in symptomatic primary HPT if medically fit
• Indications in asymptomatic primary HPT:

• Serum Ca2+ > 1.0 mg/dL = 0.25 mmol/L above upper normal limit
• Age <50 years
• Osteoporosis / reduced BMD or fragility fracture
• Renal involvement → Stones, nephrocalcinosis, reduced kidney function
• Parathyroid carcinoma suspected
• Patient preference or inability to comply with observation

2. Secondary Hyperparathyroidism

• First-line → Treat underlying cause + medical treatment
• Surgery if refractory to medical therapy
• Typical indications → Severe bone disease, fractures, pruritus, calciphylaxis, progressive soft-tissue/vascular calcification

3. Tertiary Hyperparathyroidism

• Surgery if persistent autonomous PTH secretion causes hypercalcemia
• Indications → Symptomatic hypercalcemia, renal/bone complications, graft dysfunction risk, failed medical therapy

Types of Parathyroid Surgery

1. Focused / Minimally Invasive Parathyroidectomy

• For localized single adenoma
• Guided by preoperative localization: US, sestamibi, 4D-CT if needed
• Often uses intraoperative PTH monitoring
• PTH fall after excision → Suggests cure

2. Bilateral Neck Exploration

• Traditional approach → Explore both sides, identify all 4 glands if possible
• Use when localization is negative/discordant or multiglandular disease suspected
• Also useful in familial/MEN disease or complex/reoperative anatomy

3. Subtotal Parathyroidectomy

• Removal of 3.5 glands
• Used for hyperplasia, secondary/tertiary HPT, hereditary multigland disease
• Goal → Prevent recurrence while avoiding permanent hypoparathyroidism

4. Total Parathyroidectomy with Autotransplantation

• Remove all glands
• Implant small parathyroid tissue into forearm muscle or sternocleidomastoid
• Used in severe hyperplasia or recurrent renal hyperparathyroidism

5. Parathyroid Carcinoma

• Rare; suspect if very high Ca2+/PTH, hard neck mass, local invasion or RLN palsy
• Treatment → En bloc resection with ipsilateral thyroid lobe/involved tissue if needed
• Avoid capsular rupture

Postoperative Care and Surgical Complications

1. Hypocalcemia / Hungry Bone Syndrome

• Sudden PTH drop after operation → Calcium shifts into bone
• Symptoms → Perioral numbness, tingling, muscle cramps, tetany
• Management → Monitor Ca2+/PTH; calcium + vitamin D supplementation

2. Recurrent Laryngeal Nerve Injury

• Close relation to thyroid/parathyroid glands
• Unilateral injury → Hoarseness/vocal cord palsy
• Bilateral injury → Airway obstruction risk

3. Other Follow-Up Points

• Bleeding/neck hematoma → Airway emergency
• Persistent high PTH/Ca2+ → Missed gland, multigland disease or ectopic gland
• Long-term follow-up → Serum Ca2+ and PTH for recurrence

IV. Medical Treatment

Medical Treatment

1. Primary Hyperparathyroidism if Surgery Deferred/Contraindicated

• Hydration; avoid dehydration
• Maintain vitamin D sufficiency
• Calcimimetic: cinacalcet → Increases Ca2+-sensing receptor sensitivity → Decreases PTH/serum Ca2+
• Bisphosphonates or denosumab → Inhibit bone resorption, improve BMD
• Monitoring → Ca2+, renal function, BMD, renal stones

2. Secondary Hyperparathyroidism

• Treat underlying cause: CKD/mineral disorder, vitamin D deficiency, malabsorption
• Dietary phosphate restriction + phosphate binders → Decrease GI phosphate absorption
• Vitamin D analogues / calcitriol → Suppress PTH secretion
• Calcimimetic: cinacalcet → Decreases PTH