Endocrinology — 5-min cram sheet — TheStudyFix Medical Library

Written by Betra Youhanna, a medical student and not a doctor — check every detail against your own teaching.

A quick revision sheet. Check current teaching and clinical guidance before using any detail in patient care.

Endocrinology — 5-min cram sheet

_Built from the endo disease index. Deck-faithful._

Buzzword → answer (the vignette reflex)

Acetone (fruity) breath + Kussmaul respiration → DKA (mostly T1DM)
Explosive onset in a young lean patient with ketoacidosis → T1DM (diagnostic)
Bronze hyperpigmentation + hyponatraemia + hyperkalaemia + hypoglycaemia → Addison's (primary adrenal insufficiency)
"Spells"/paroxysms — headache, perspiration, palpitations, pallor → Phaeochromocytoma (5 Ps)
Purple striae + moon face + buffalo hump + thin arms & legs → Cushing's syndrome
Chvostek + Trousseau signs → Hypocalcaemia (pathognomonic of neuromuscular excitability)
"Stones, bones, groans, moans" → Hypercalcaemia
Non-pitting myxedema + loss of outer ⅓ eyebrows (Queen Anne's sign) + slow-relaxing reflexes → Hypothyroidism
Pretibial myxedema + diffuse goitre + bruit + exophthalmos → Graves' disease (pretibial myxedema pathognomonic)
Exquisitely tender thyroid + ESR up to 100 + low RAI uptake → Subacute (de Quervain's) thyroiditis
Orphan Annie-eyed nuclei on FNA → Papillary thyroid carcinoma
Amyloid stroma + high calcitonin → Medullary thyroid carcinoma (parafollicular C-cell)
Hürthle cells + lymphocytic infiltration on FNA → Hashimoto's thyroiditis
Rib notching + "three sign" on CXR + arm–leg BP discrepancy → Coarctation of the aorta
Mucosal neuromas (lips/tongue) + marfanoid habitus → MEN 2B
Craving cold liquids + polyuria (>3 L/day) → Diabetes insipidus
Pemberton's sign (arms overhead → facial plethora + JVD) → Retrosternal goitre
Whipple's triad (symptoms + low glucose + relief on raising glucose) → Hypoglycaemia
Elderly obese woman in winter, hypothermia, hoarse voice, coma → Myxedema coma (sepsis = #1 precipitant)

Dynamic test / hormone pattern → diagnosis

Test / pattern	Result	Diagnosis
Overnight 1 mg DST	Not suppressible (cortisol >1.8 mcg/dL / >50 nmol/L)	Cushing's syndrome
High-dose DST (2 mg q6h)	Pituitary suppresses, ectopic does not	Cushing's disease vs ectopic ACTH
Short synacthen (250 µg)	Peak cortisol >18–20 mcg/dL (>550 nmol/L)	Excludes primary adrenal failure
Water deprivation → desmopressin	Fails to concentrate, then urine osmo rises ≥50%	Central (cranial) DI
Water deprivation → desmopressin	No change on deprivation AND no change with desmopressin	Nephrogenic DI
Water deprivation	Urine markedly concentrates	Psychogenic polydipsia
OGTT	GH fails to suppress (>10 ng/mL after oral glucose)	Acromegaly
Aldosterone/Renin ratio	Elevated — high aldosterone, low renin	Primary hyperaldosteronism (Conn's)
Renin + aldosterone	High renin + high aldosterone	Secondary hyperaldosteronism
Adrenal vein sampling (aldo/cortisol)	>4 = adenoma (surgical); <3 = bilateral hyperplasia (medical)	Localises Conn's
ITT (GH/cortisol)	Failure to rise (valid only if glucose <2.5 mmol/L)	GH deficiency
Calcitonin	>100 pg/L (100% PPV); >400 suggests distant mets	Medullary thyroid carcinoma
Ca + PTH	High Ca + high/inappropriately-normal PTH	Primary hyperparathyroidism
Ca + PTH	High Ca + suppressed PTH (→ PTHrP)	Malignancy / non-parathyroid hypercalcaemia
TSH + T4/T3	↑TSH ↓T4 primary hypo · ↓TSH ↑T4 primary hyper · ↓TSH ↓T4 central · ↑TSH ↑T4 TSH-oma	TFT interpretation
ACTH + cortisol	↓cort/↑ACTH Addison's · ↓cort/↓ACTH steroid or hypopituitarism · ↑cort/↑ACTH Cushing's disease OR ectopic · ↑cort/↓ACTH adrenal adenoma	ACTH/cortisol patterns
Radioiodine scan	Diffuse hot = Graves · multiple hot/patchy = toxic MNG · one super-hot = toxic adenoma · cold = 5–8% malignant	Thyrotoxicosis / nodule
RAI uptake	Nil neck uptake + low thyroglobulin	Thyrotoxicosis factitia

Criteria / staging / scores at a glance

Diabetes dx — FPG ≥7.0 mmol/L (126) · A1C ≥6.5% (not valid in suspected T1DM) · 2h-OGTT ≥11.1 (200) · random ≥11.1 + symptoms. Asymptomatic → repeat on another day.
Prediabetes — IFG FPG 6.1–6.9 · IGT 2h-PG 7.8–11.0 · A1C 6.0–6.4%.
GDM screening (24–28 wks) — one-step 75g (fasting ≥92 / 1h ≥180 / 2h ≥153 mg/dL, any one) OR two-step 50g GLT → if 1h ≥130–140 → 100g OGTT (≥2 values).
DKA — glucose >250 mg/dL · bicarbonate <15 mEq/L · pH <7.3 · ketonaemia + ketonuria (triad: hyperglycaemia + ketosis + metabolic acidosis).
HHS — glucose >600 mg/dL · osmolarity >310 mOsm/L · dehydration + depressed sensorium · NO ketoacidosis.
DM targets — A1C <7.0% · preprandial 90–130 · postprandial <180 mg/dL · BP <130/80 · LDL <100 / TG <150 / HDL >40 mg/dL.
Acromegaly OGTT — GH >10 ng/mL after oral glucose = diagnostic; normal glucose suppresses GH; IGF-1 elevated.
Cushing's screening — overnight 1 mg DST, <1.8 mcg/dL (50 nmol/L) excludes; 24h urinary free cortisol elevated; loss of cortisol circadian rhythm.
DST variants — overnight low-dose 1–2 mg (screen) · 48h low-dose 0.5 mg q6h (confirm) · 48h high-dose 2 mg q6h (localise); failure to suppress = cortisol >50 nmol/L.
Synacthen — short 250 µg IV, peak >550 nmol/L (>18 mcg/dL) excludes primary; long depot ×3 days differentiates primary vs secondary.
Water deprivation — DI confirmed if plasma osmo >300 with urine osmo <600 (stop if weight ↓3%).
ITT — gold standard GH/cortisol reserve; valid only if glucose <2.5 mmol/L; contraindicated in epilepsy / IHD.
GH deficiency cutoffs — adult deficient <2.7 (not deficient >6) µg/L · child deficient <4.5 (not deficient >7.5) µg/L.
Diabetes classification (ADA) — 4 classes: Type 1 · Type 2 · Gestational · Specific types (monogenic, exocrine pancreas, drug/chemical).
CAH enzymes — 21-OH (90%): ↓mineralocorticoid, ↑androgens, marker 17-OH-progesterone, low BP (salt-wasting) · 11β-OH: ↑DOC, ↑androgens, marker 11-deoxycortisol, high BP · 17α-OH: ↑mineralocorticoid, ↓androgens, high BP, undervirilised ♂. Autosomal recessive.
Hyperaldosteronism — Primary (Conn's): low renin/high aldo · Secondary: high renin/high aldo · Pseudo: low renin/low aldo (Cushing's, liquorice, SAME, Liddle's). All → HTN.
MEN — MEN 1 (3 Ps: Pituitary+Parathyroid+Pancreatic, Menin gene) · MEN 2A (MTC+Phaeo+HyperPTH, RET) · MEN 2B (MTC+Phaeo+mucosal neuromas+marfanoid, no PHPT, RET) · FMTC (MTC only, RET). MEN 2 = AD, ~100% penetrance.
Polyglandular autoimmune — Schmidt (Addison + Hashimoto) · PAS-1 (APECED, AIRE gene, AR: Addison + hypoPTH + mucocutaneous candidiasis) · PAS-2 (Addison + T1DM + Hashimoto's/Graves').
Rule of 10s (phaeo) — 10% extra-adrenal / bilateral / malignant / familial / normotensive.
TFT patterns — TSH normal range 0.5–5 µU/ml; assess with free hormone.
ACR TI-RADS scoring — taller-than-wide = 3 pts · punctate echogenic foci = 3 · very hypoechoic = 3 · extra-thyroidal extension = 3.
TI-RADS categories & FNA — TR1 0.3% (no FNA) · TR2 1.5% (no) · TR3 4.8% (FNA ≥2.5 cm) · TR4 9.1% (≥1.5 cm) · TR5 35% (≥1.0 cm). Follow-up: TR3 ≥1.5 · TR4 ≥1.0 · TR5 ≥0.5 cm.
Bethesda FNA — I non-diagnostic 5–10% · II benign 0–3% · III AUS/FLUS 6–18% · IV follicular neoplasm 10–40% · V suspicious 45–60% · VI malignant 94–96%. Molecular testing (ThyroSeq) avoids surgery in ~60% of III/IV.
NO SPECS (Graves' eye) — 0 none · 1 signs only (lid retraction/lag) · 2 soft tissue · 3 proptosis · 4 extraocular muscle · 5 corneal · 6 sight loss.
Thyroid cancer prognosis — Papillary (5% 10-yr mortality, 96% 5-yr survival) > Follicular (10%, 91%) > Hürthle (15%) > Medullary (20%, 85%) > Anaplastic (7% 5-yr survival).
ATA post-op risk (WDTC) — Low: no RAI, TSH 0.5–2.0 · Intermediate: 30 mCi, TSH 0.1–0.5 · High: 100–150 mCi, TSH <0.1 mU/L.
Hyperparathyroidism — Primary: ↑Ca ↓PO4 ↑PTH (adenoma) · Secondary: ↓/normal Ca ↑PO4 ↑PTH (CKD) · Tertiary: ↑Ca ↑PO4 very-↑PTH (post-transplant, autonomous).
DEXA / FRAX — T-score <−2.5 = osteoporosis (osteopenia −1 to −2.5); Z-score flags secondary osteoporosis; FRAX = 10-yr fracture probability (Red = treat / Orange = measure BMD / Green = reassure).
Parathyroidectomy (asymptomatic PHPT), any one — age <50 · Ca >1 mg/dL over ULN · CrCl <60 · T-score <−2.5 · 24h urine Ca >400 mg · vertebral fracture/nephrolithiasis/nephrocalcinosis · unable/unwilling for surveillance.
Hypercalcaemic crisis — corrected Ca >3.5 mmol/L; normal saline up to 200 mL/h; avoid diuretics; pamidronic acid 60–90 mg IV; delay surgery until Ca <3 mmol/L.
T2DM step-up — monotherapy (metformin) → dual (+1 agent if A1C not met after ~3 mo or ≥9%) → triple (+2 agents) → insulin if A1C <7% not reached on max orals.

Discriminators that decide questions

T1DM vs T2DM — T1: islet autoantibodies usually present, C-peptide undetectable/low, first-line insulin, DKA common; T2: antibodies absent, C-peptide normal/high, non-insulin agents, DKA rare.
DKA vs HHS — DKA: glucose >250, bicarb <15, pH <7.3, ketones present (mostly T1DM); HHS: glucose >600, osmolarity >310, NO significant ketoacidosis (mostly T2DM, enough insulin to suppress ketogenesis but not hyperglycaemia).
Primary vs secondary hyperaldosteronism — Primary (Conn's): low renin / high aldosterone (inverse); Secondary: high renin + high aldosterone (direct, e.g. renal artery stenosis; normotensive causes = Gitelman's/Bartter's).
Primary vs secondary adrenal insufficiency — Primary (Addison's): pigmented + salt-wasting, high ACTH, aldosterone low/renin high, needs fludrocortisone; Secondary: not pigmented, no salt-wasting, low/inappropriately-normal ACTH, aldosterone preserved, NO fludrocortisone.
Central vs nephrogenic DI — Central: desmopressin makes urine concentrate (ADH secretion deficit); Nephrogenic: desmopressin → no change (end-organ ADH unresponsiveness — lithium, hypercalcaemia, hypokalaemia).
Papillary vs follicular carcinoma — Papillary: lymphatic spread, multifocal, Orphan Annie nuclei, good prognosis; Follicular: bloodstream (haematogenous) spread, unifocal, capsular/vascular invasion diagnostic, worse prognosis.