Parathyroid Glands Anatomy

Parathyroid Glands

• There are 4 parathyroid glands, 2 on the right and 2 on the left side of the neck.
• They secrete the hormone parathormone (PTH) independently of the pituitary gland.
• Parathyroid glands are typically yellow/brown in color, described as "Portland brick."
• In children, they are pinkish, and in adults, they are golden-yellow to light brown.

Superior Parathyroids

• Derived from the endoderm of the 4th branchial arch.
• Develop along with the thyroid gland.
• Located in the middle of the posterior aspect of the thyroid gland, in relation to the inferior thyroid artery.
• Constant in position, smaller (20-40 mg), and dorsal to the recurrent laryngeal nerve (RLN).

Inferior Parathyroids

• Derived from the endoderm of the 3rd branchial arch (with thymus).
• Not constant in position.
• May be located in the lower pole, within the fascial sheath of the thyroid gland, low down in the neck, or outside the fascial sheath.
• Larger (30-50 mg) and ventral to the RLN.

Causes of Tetany

• Hypoparathyroidism.
• Severe respiratory alkalosis.
• Low calcium levels.
• Osteomalacia and rickets due to vitamin D deficiency.
• Hypokalaemic alkalosis of pyloric stenosis.
• Following massive transfusion (citrate overload).

Signs and Symptoms of Tetany

• Tingling and numbness of the fingers, toes, lips, and occasionally, circumoral pallor.
• Cramps of the hands and feet.
• Carpopedal spasm.
• Stridor.
• Latent tetany can be diagnosed by Chvostek's sign and Trousseau's sign.
• Spasm of intraocular muscles results in blurring of vision.
• Convulsions.

Hyperparathyroidism (HPT)

• An uncommon disease that occurs due to parathyroid activity, manifesting as hypercalcaemia.
• Primary hyperparathyroidism (PHPT) can be caused by genetic mutations, lithium, and low-dose therapeutic ionizing radiation.
• Renal leak of calcium and declining renal function with age may also be causative factors for PHPT.

Primary Hyperparathyroidism (PHPT)

• Familial/genetic: Can be part of MEN syndrome - I and MEN IIA, or familial PHPT with jaw tumor syndrome.
• Exact cause of primary hyperparathyroidism is unknown.
• Lithium is associated with parathyroid hyperplasia and primary HPT.

Symptoms of Hyperparathyroidism

• Painful bones (bone disease).
• Renal stones (renal disease).
• Abdominal groans.
• Psychiatric moans.
• Fatigue overtones.
• Abdominal pain.
• Oliguria.
• Corneal calcification/band keratopathy.
• Proximal myopathy.
• Muscle wasting.

Investigations

• SPECT: Useful in evaluating ectopic parathyroid adenomas.
• Serum calcium levels are always raised above normal limits (9-11 mg%).
• Albumin is the main calcium-binding protein in the plasma and should be measured.
• Serum PTH level is estimated by immunoassay and is the diagnostic investigation.
• Serum phosphorus levels are decreased.
• Alkaline phosphatase is increased when bones are involved.

Indications for Surgery

• All symptomatic patients should be offered surgery.
• Types of surgery include:
  • Single adenoma: Excision of the gland and removal of one normal parathyroid gland for histopathological study.
  • Diffuse hyperplasia: Removal of 3 or 3 parathyroids and autotransplantation into the forearm muscle tissue.
  • Carcinoma: Removal of all four glands, along with the ipsilateral thyroid lobe, and modified radical neck dissection in the presence of lymph node metastasis.