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Parathyroid Disorders Overview

Jun 10, 2025

Overview

This lecture reviews parathyroid gland physiology and disorders, focusing on two patient cases to illustrate hypoparathyroidism and primary hyperparathyroidism.

Patient Cases

  • Melania (47): Post-thyroidectomy, presented with tetany and positive Chvostek sign; labs showed low calcium, high phosphate, low PTH.
  • Emma (55): Presented with constipation, muscle weakness, bone pain, depression, and history of calcium kidney stones; labs showed high calcium, low phosphate, high PTH.
  • Melania diagnosed with hypoparathyroidism due to surgical removal of parathyroid glands.
  • Emma diagnosed with primary hyperparathyroidism due to a PTH-secreting adenoma.

Parathyroid Physiology

  • Four parathyroid glands regulate blood calcium via PTH secretion.
  • Chief cells in parathyroids detect extracellular calcium and phosphate changes.
  • Low calcium/high phosphate stimulate PTH release.
  • PTH increases blood calcium by mobilizing bone stores, increasing renal reabsorption, reducing phosphate, and activating vitamin D for GI absorption.

Hypoparathyroidism

  • Most commonly caused by accidental removal during thyroid surgery.
  • Other causes: autoimmune destruction, DiGeorge syndrome (failure of pharyngeal pouch development).
  • Pseudohypoparathyroidism: end-organ resistance to PTH (e.g., Albright hereditary osteodystrophy).
  • Symptoms: hypocalcemia, hyperphosphatemia, tetany, +Chvostek and Trousseau signs, possible severe seizures/arrhythmias.

Hyperparathyroidism

  • Primary: Parathyroid adenoma (most common), hyperplasia, or carcinoma lead to high PTH.
  • Symptoms: "Stones" (kidney stones), "Thrones" (polyuria), "Bones" (bone pain), "Groans" (constipation, muscle weakness), "Psychiatric overtones" (depression, confusion).
  • Lab findings: Hypercalcemia, hypophosphatemia, high PTH, high alkaline phosphatase, high urinary cAMP.
  • Secondary: Compensatory rise in PTH due to chronic hypocalcemia (e.g., chronic kidney disease).
  • Tertiary: Autonomous PTH secretion after prolonged secondary hyperparathyroidism, leading to hypercalcemia.
  • Familial hypocalciuric hypercalcemia (FHH): Defective calcium sensing, mild hypercalcemia, hypocalciuria, mildly elevated PTH.

Key Terms & Definitions

  • Thyroidectomy — surgical removal of the thyroid gland.
  • Parathyroid hormone (PTH) — hormone regulating calcium and phosphate balance.
  • Tetany — involuntary muscle contractions due to hypocalcemia.
  • Chvostek sign — facial muscle twitch after facial nerve tap, indicating hypocalcemia.
  • Trousseau sign — carpopedal spasm with blood pressure cuff, indicating hypocalcemia.
  • Albright hereditary osteodystrophy — genetic PTH resistance, with bone deformities.
  • Osteitis fibrosa cystica — bone lesions from excessive PTH.

Action Items / Next Steps

  • Review physiology and pathophysiology of parathyroid disorders.
  • Study causes, symptoms, and lab findings of hypo- and hyperparathyroidism.
  • Practice clinical cases distinguishing parathyroid disorders.

Full transcript