PSPal Surgery

Calcium & the parathyroid

Four glands that together weigh less than a paperclip, defending one number minute by minute — and every calcium problem a surgeon meets is that defence working too hard, or not at all.

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 .

Calcium is one of the few things the body holds inside a band barely one and a half milligrams per decilitre wide. Learn the loop that defends it and the clinical problems stop being a list to memorise: each one is a single step of the circuit failing.

PARATHYROID GLANDS CaSR senses · chief cell secretes PTH BONE osteoblast → RANKL → osteoclast releases calcium + phosphate KIDNEY reabsorbs calcium, wastes phosphate 1α-hydroxylase ON → calcitriol GUT calcitriol builds the transporters absorbs calcium + phosphate PLASMA IONISED CALCIUM defended within a narrow band calcium FALLS→ PTH released calcium RISES → PTH switched off
Four glands watch one number. One hormone acts on three organs. Every action returns calcium to the plasma, and the rising calcium switches the hormone off.

Start here

Free toolCorrected calcium calculator Enter the calcium and the albumin and get the corrected value, in mg/dL or mmol/L, with what it means. The diagnosis Causes of hypercalcaemia Three numbers — calcium, PTH, phosphate — sort every cause into four quadrants, and only one of them is surgical. The surgical disease Primary hyperparathyroidism One gland in 85% of patients, the criteria that decide an operation, and what the surgeon finds in the neck. On the ward Tingling fingers after neck surgery The calcium problem you are most likely to manage yourself as an intern — and the timeline that explains why a normal result at six hours proves nothing. Emergency Hypercalcaemic crisis Fluids first, always. Why the loop diuretic is the wrong reflex, and what order the rest comes in. Free book · 35 pagesCalcium & the Parathyroid The whole circuit and the whole patient, illustrated, with five worked cases.

The one sentence to carry

Ninety-nine per cent of body calcium is in bone. Of the plasma calcium, about half is ionised and physiologically active, about forty per cent is bound to albumin, and the remainder is complexed to anions. Only the ionised fraction is regulated, so a total calcium must always be read alongside the albumin.

Where this fits with the thyroid

The two subjects share a patient. The woman having a total thyroidectomy on Monday is a thyroid case until Tuesday morning, when her fingers start tingling and she becomes a calcium case. If you are revising one, revise the other — endocrine and bariatric surgery covers the neck lump and the thyroid status history that comes before the operation.

Related pages

ToolCorrected calciumAlbumin changes the number, not the disease.TopicEndocrine surgeryThe neck lump and the thyroid history.PracticeClerk a patientNine simulated surgical histories.Free bookCalcium & the Parathyroid35 illustrated pages, free to download.
Jaundice & liver testsWhy a patient turns yellow, how to tell the three types apart at the bedside, and how to read the liver function tests that follow.7 guides · 1 calculator · 2 casesBile & the gallbladderThe enterohepatic circulation in ten steps, what bile actually does to a fat meal, and what happens when the circuit is broken.3 guides · 1 case · book Part 1The acute abdomenThe commonest reason a student is sent to clerk a patient. Where the pain started, where it went, and what that movement tells you.3 cases to clerkGastrointestinal bleedingBlood from the top and blood from the bottom: what to ask, which drug history matters, and what must not be called haemorrhoids.2 cases to clerkHernia & the groinA lump in the groin, and the three questions that decide whether it can wait until the morning or needs a surgeon tonight.1 case to clerkEndocrine & bariatric surgeryThe thyroid, the parathyroids and the metabolic patient — the operations this unit does most, and the histories behind them.1 case · 1 peer-reviewed chapterWounds & the lower limbVenous, arterial or neuropathic. Three ulcers that look similar on a ward round and are told apart almost entirely by the history.1 case to clerk