PSPal Surgery

Calcium & the Parathyroid: A Visual Guide for Medical Students

35 illustrated pages. Volume 2 of the series. Free to download, licensed for teaching.

Written and clinically reviewed by , consultant minimally invasive and bariatric surgeon, Al-Makassed Hospital, Jerusalem, and Assistant Professor of Surgery, Al-Quds University. Last updated .

Front cover of Calcium & the Parathyroid: A Visual Guide for Medical Students by Dr. Mohammed Maree

Calcium is one of the few things the body defends minute by minute. It is held inside a band roughly one and a half milligrams per decilitre wide, and it is defended by four glands that together weigh less than a paperclip.

Almost every calcium problem a surgeon meets — the woman with recurrent stones, the man whose bones ache, the patient whose fingers tingle the night after a thyroidectomy — is that defence system either working too hard or not working at all. Read the circuit once and the clinical half stops being a list to memorise: every decision in it is one step of the circuit failing.

Download the free PDF View on Zenodo (DOI)

DOI: 10.5281/zenodo.23158993 · Licensed CC BY-NC 4.0 · Volume 2 of Visual Guides for Medical Students

What is inside

Part 1 · The calcium circuit

  1. Where the calcium is
  2. The thermostat: the calcium-sensing receptor
  3. Four glands, two origins
  4. The signal: parathyroid hormone
  5. PTH on bone
  6. PTH on the kidney: calcium in, phosphate out
  7. PTH on the kidney: making the active vitamin D
  8. Calcitriol on the gut
  9. Closing the loop
  10. The whole circuit on one page

Part 2 · The patient

  1. Reading a calcium result
  2. Three numbers, one diagnosis
  3. The patient with hypercalcaemia: history
  4. The patient with hypercalcaemia: examination
  5. What the imaging shows
  6. Primary hyperparathyroidism: the surgical disease
  7. Localisation, and the operation
  8. Hypercalcaemia of malignancy, and the crisis
  9. Secondary and tertiary hyperparathyroidism
  10. The tingling fingers: hypocalcaemia after neck surgery
  11. Five questions at the bedside

Part 3 · Five patients

  • The stone that led to the neck — a preoperative diagnosis, worked step by step
  • The PTH that did not fall — in the operating theatre
  • The operation that should never happen — familial hypocalciuric hypercalcaemia
  • Day one after a total thyroidectomy — hypocalcaemia
  • Eighteen months after the new kidney — tertiary hyperparathyroidism

The four milestones

  • M1 — Describes the calcium circuit and names the actions of PTH
  • M2 — Interprets a calcium, PTH and phosphate panel and reaches a diagnosis
  • M3 — Assesses a patient with hypercalcaemia: history, examination, first-line investigations
  • M4 — Acts as an intern: recognises hypercalcaemic crisis and post-thyroidectomy hypocalcaemia, starts first-line treatment, and escalates appropriately

A note on units

All values in the book are given in mg/dL, matching the chemistry report handed to you on the ward, with the conversion to mmol/L alongside. The reference intervals are printed in full on page 17 — check them against your own laboratory's sheet before quoting them in an exam or a clinic letter. The corrected calcium calculator on this site works in either set of units.

Who it is for

Medical students on a surgical or endocrine rotation, students preparing for an OSCE, interns, and junior surgical trainees. It assumes no prior knowledge and builds from the physiology upwards. Read Part 1 before the endocrine tutorial, and Part 2 alongside the thyroid and neck-lump station.

How to cite it

Maree M. Calcium & the Parathyroid: A Visual Guide for Medical Students. 1st ed. Visual Guides for Medical Students, Volume 2. Zenodo; 2026. doi:10.5281/zenodo.23158993

Read it online instead

Topic hubCalcium & the parathyroid The circuit, and every page built on it. Free tool Corrected calcium calculator In mg/dL or mmol/L, with the formula and a worked example. Diagnosis Causes of hypercalcaemiaThree numbers, four quadrants. Ward The tingling fingersThe calcium emergency you will manage yourself.

Using it in teaching

The licence is CC BY-NC 4.0. You may share, print and adapt it for non-commercial teaching, provided the author is credited. If you use it with a student group, I would be glad to hear how it went.