Hyperparathyroidism

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Physiology of Calcium metabolism:

Types & Causes:

  1. Primary hyperparathyroidism:
    • Parathyroid adenoma (overall MC cause), MC site: Inferior parathyroid
    • Parathyroid hyperplasia.
  1. Secondary hyperparathyroidism:
    • CKD
    • Vitamin D deficiency.
  1. Tertiary hyperparathyroidism:
    • Long standing CKD → Parathyroid hyperplasia → Adenoma.
  1. Pseudohyperparathyroidism:
    • Hypercalcemia of malignancy
    • Paraneoplastic syndrome due to PTHrP (PTH related peptide)
    • MC-ly seen with squamous cell carcinoma of lung.

 

Primary hyperparathyroidism (PHPT)

  • It is the MC cause of chronic hypercalcemia
  • Pathophysiology: ↑PTH → ↑Serum calcium
  • Clinical features:
    • Primary hyperparathyroidism is mostly asymptomatic
    • Clinical features of hypercalcemia may be seen:
      1. Bones: Bone pain, pathological fractures, Brown’s tumor, Osteitis fibrous cystica
      2. Stones: Recurrent/ multiple renal stones
      3. Abdominal groans: Colicky pain, Pancreatitis
      4. Psychiatric moans: Psychosis.

Radiological features of long-standing hyperparathyroidism:

  1. X-ray skull: Salt & pepper skull
  2. Subperiosteal resorption of radial side of 2nd & 3rd digits.

Biochemical picture:

  • Serum PTH: High
  • Serum calcium: High
  • Serum phosphorus: Low.

Diagnosis:

If getting the above biochemical picture, send the patient for an USG neck (BEST is Sestamibi scan):

  1. If only 1 gland is enlarged: Adenoma
  2. If all 4 glands are enlarged: Hyperplasia.

Treatment:

Surgery is preferred for:

  1. All symptomatic patients
  2. Asymptomatic patient with age <50 years, serum calcium 1 mg/dl above the baseline and/or features of osteoporosis/ renal stone.

Surgery:

  1. Adenoma: Remove only adenomatous gland
  2. Hyperplasia: Remove 3 & ½ glands. Remaining ½ gland is removed, minced into small pieces and inserted into brachioradialis of non-dominant hand/ SCM muscle.Advantage of this method: If there is a recurrence, we can remove the gland under local anesthesia as we already know the site where we have implanted.
  1. A thymectomy should be routinely undertaken for patients with MEN 1-associated PHPT or in secondary hyperparathyroidism.

Special note: Hungry bone syndrome after parathyroidectomy:

  • Initial pathology was Hyperparathyroidism, stimulating both osteoblasts and osteoclasts
  • After parathyroidectomy, the stimulation to osteoclasts go away first but osteoblasts remain activated for few weeks → In this time, ↑serum calcium is taken by bone → Resulting in hypocalcemia
  • As bone takes more calcium in this period, this is known as “Hungry bone syndrome”.

All other asymptomatic patients should undergo medical management for correction of hypercalcemia:

  1. Hydration
  2. Diuretics (Loop diuretics → Furosemide)
  3. Bisphosphonate (inhibition of osteoclastic activity); Limitation: Delayed onset of action, takes 24-48 hours to show effect
  4. Calcitonin
  5. Dialysis.

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