Endocrinology

Parathyroid and Calcium Disorders

Clinical overview and exam mastery guide for PTH-driven calcium disorders, hyper/hypocalcemia treatment, and CKD-related mineral management.

PTH Effect
Raises serum calcium
Primary HyperPTH
High calcium, low phosphate
Severe Hypercalcemia
Fluids then antiresorptive
Acute Hypocalcemia
IV calcium gluconate

Calcium Regulation Core

PTH bone and kidney raise calcium Vitamin D gut absorption bone support Calcitonin short-term calcium lowering Clinical approach: identify direction and urgency Hypercalcemia and hypocalcemia need different urgency pathways

Interpret PTH-calcium-phosphate together for rapid classification.

1. Calcium Physiology (Foundation First)

Calcium homeostasis is mainly regulated by parathyroid hormone, vitamin D, and calcitonin.

PTH

  • Released when calcium is low
  • Increases bone resorption
  • Increases renal calcium reabsorption
  • Increases phosphate excretion

Vitamin D

  • Increases intestinal calcium absorption
  • Supports bone mineralization

Net Effect

PTH response raises serum calcium.

2. Hyperparathyroidism

Types and Pattern

  • Primary: adenoma most common
  • Secondary: CKD or vitamin D deficiency
  • Primary labs: high calcium, low phosphate

Clinical Features

  • Kidney stones, bone pain, abdominal symptoms
  • Neuropsychiatric symptoms
  • Classic memory phrase: stones, bones, groans, psychiatric overtones
Primary hyperparathyroidism is managed surgically when symptomatic or significantly elevated.

Cinacalcet (for selected non-surgical/CKD contexts)

  • MOA: calcimimetic, increases sensitivity of calcium-sensing receptor and lowers PTH secretion
  • Side effects: hypocalcemia, nausea
  • Contraindication: baseline hypocalcemia

3. Hypoparathyroidism

Causes and Features

  • Post-thyroidectomy, autoimmune disease, magnesium deficiency
  • Tetany, cramps, seizures, prolonged QT

Treatment

  • Calcium supplementation
  • Active vitamin D (calcitriol)
Drug MOA Major Side Effects Notes
Calcium supplementation Direct calcium replacement Constipation, hypercalcemia if overcorrected Titrate with serial calcium monitoring
Calcitriol Active vitamin D, increases intestinal calcium absorption Hypercalcemia Used with calcium in chronic replacement plans

4. Hypercalcemia

Common Causes and Features

  • Hyperparathyroidism, malignancy, thiazides, vitamin D excess
  • Weakness, confusion, polyuria, constipation

Severity-Based Management

  • Mild: hydration and cause-directed therapy
  • Severe: IV fluids first, then loop diuretic if needed, plus antiresorptive treatment
Agent MOA Major Side Effects Notes
Bisphosphonates (zoledronic acid) Inhibit osteoclast-mediated bone resorption Hypocalcemia, osteonecrosis of jaw (rare) Key for malignancy-related hypercalcemia
Calcitonin Inhibits osteoclast activity and lowers calcium rapidly Nausea, flushing, tachyphylaxis with ongoing use Short-term bridge agent

5. Hypocalcemia

Causes and Signs

  • Hypoparathyroidism, CKD, vitamin D deficiency, pancreatitis
  • Chvostek sign, Trousseau sign, tetany

Treatment

  • Acute symptomatic: IV calcium gluconate
  • Chronic: oral calcium plus vitamin D

Management Recap Drill

Primary hyperparathyroidism: surgery when indicated or cinacalcet in selected non-surgical cases.
Hypoparathyroidism: calcium plus calcitriol replacement.
Severe hypercalcemia: IV fluids then antiresorptive therapy.
Acute hypocalcemia: IV calcium.

Visual Algorithm Placeholder

[Insert Calcium Disorder Diagnostic and Treatment Algorithm Here During UI Integration]

Guideline References (Management)

Endocrine Society Clinical Practice Guidelines

https://www.endocrine.org

Guideline Scope

  • Hyperparathyroidism management
  • Hypocalcemia treatment
  • CKD-related mineral disorder approaches

6. Common Exam Traps

Primary hyperparathyroidism usually shows high calcium with low phosphate.
Cinacalcet lowers PTH by increasing calcium-sensing receptor sensitivity.
Bisphosphonates are central for hypercalcemia of malignancy.
Calcitonin acts quickly but loses effect with prolonged use.
Hypocalcemia can present with prolonged QT and tetany signs.

7. Quick Revision Summary

Must Remember

  • PTH raises calcium
  • Hyperparathyroidism drives hypercalcemia
  • Hypoparathyroidism drives hypocalcemia
  • Severe hypercalcemia needs fluids plus antiresorptive strategy
  • Acute symptomatic hypocalcemia needs IV calcium

Practice Questions Placeholder

  • Topic: Parathyroid and Calcium Disorders
  • Subtopics: hyperparathyroidism, hypoparathyroidism, hypercalcemia, hypocalcemia, CKD mineral disorder