Master Endocrinology & Diabetes
for PLAB 1

What the PLAB 1 Tests in Endocrinology & Diabetes

The PLAB 1 exam tests your ability to manage common endocrine and diabetic presentations in a UK clinical setting. You must demonstrate knowledge of diagnostic criteria (e.g., HbA1c ≥48 mmol/mol for diabetes), first-line pharmacotherapy (e.g., metformin for type 2 diabetes, levothyroxine for hypothyroidism), and acute management (e.g., DKA protocol, Addisonian crisis). Questions often focus on interpreting thyroid function tests, recognising complications like diabetic foot ulcers or hypoglycaemia unawareness, and selecting appropriate specialist referrals. You are expected to know NICE/RCGP guidelines for monitoring, screening (e.g., annual diabetic retinopathy), and perioperative management of diabetes. The exam emphasises safe prescribing, recognising red flags (e.g., thyroid storm, phaeochromocytoma), and understanding when to involve endocrinology.

High-Yield Concepts

• Diabetes Diagnosis and Monitoring: Diagnosis: fasting glucose ≥7.0 mmol/L, random glucose ≥11.1 mmol/L, or HbA1c ≥48 mmol/mol (6.5%). Monitoring: HbA1c target generally 48-53 mmol/mol (6.5-7.0%) for most adults with type 2 diabetes; individualise. Annual review includes foot check (monofilament), retinal screening, renal function (eGFR, ACR), and cardiovascular risk assessment.
• Diabetic Ketoacidosis (DKA) Management: DKA criteria: glucose >11.0 mmol/L, ketones ≥3.0 mmol/L, pH <7.3, bicarbonate <15 mmol/L. First-line: IV fluids (0.9% saline), fixed-rate insulin infusion (0.1 units/kg/hr), and IV potassium replacement (20-40 mmol/L per litre). Monitor capillary ketones hourly; aim for ketone drop >0.5 mmol/L/hr. Convert to subcutaneous insulin when ketones <0.3 mmol/L and pH >7.3.
• Hypoglycaemia Management: Conscious patient: oral glucose (e.g., 15-20 g glucose tablets, 150-200 mL fruit juice). Unconscious or unable to swallow: IM glucagon 1 mg (adult) or IV 50 mL of 50% glucose. Recheck glucose after 15 minutes; if still <4.0 mmol/L, repeat. Once stable, give long-acting carbohydrate (e.g., biscuit, milk). Driving DVLA rules: inform DVLA if on insulin or sulfonylureas, must check glucose before driving.
• Thyroid Function Tests Interpretation: Primary hypothyroidism: raised TSH, low FT4. Primary hyperthyroidism: low TSH, raised FT4 (or FT3). Subclinical hypothyroidism: raised TSH, normal FT4. In sick euthyroid syndrome (non-thyroidal illness): low TSH, low FT4, low FT3. Always check anti-TPO antibodies if autoimmune thyroiditis suspected. Amiodarone can cause both hypo- and hyperthyroidism.
• Addisonian Crisis (Adrenal Insufficiency): Suspect in unexplained hypotension, hyponatraemia, hyperkalaemia, hypoglycaemia, and hyperpigmentation. Acute management: IV 100 mg hydrocortisone stat, then 100 mg 6-hourly; IV 0.9% saline (1 L over 1 hour, repeat as needed); IV dextrose if hypoglycaemic. Long-term: oral hydrocortisone (15-25 mg/day in divided doses) and fludrocortisone (50-200 mcg/day). Sick day rules: double or triple oral dose during illness.
• Cushing's Syndrome Screening: First-line: overnight dexamethasone suppression test (1 mg dexamethasone at 11pm; measure serum cortisol at 8am; normal <50 nmol/L). If abnormal: 24-hour urinary free cortisol or late-night salivary cortisol. Confirm with CRH stimulation or high-dose dexamethasone test. Causes: pituitary adenoma (Cushing's disease), adrenal adenoma, ectopic ACTH (e.g., small cell lung cancer).
• Osteoporosis Management: Diagnosis: DXA scan T-score ≤ -2.5 at hip or spine. FRAX tool for 10-year fracture risk. First-line treatment: oral bisphosphonates (e.g., alendronate 70 mg weekly) with calcium and vitamin D supplementation. Monitor renal function (eGFR >35 mL/min for bisphosphonates). Alternatives: denosumab, teriparatide, raloxifene. Review adherence and consider referral to fracture liaison service.
• Diabetes and Perioperative Care: For elective surgery: stop metformin on day of surgery (risk of lactic acidosis), stop SGLT2 inhibitors 48-72 hours pre-op (risk of euglycaemic DKA). For insulin-treated patients: reduce long-acting insulin (e.g., 80% of usual dose) or use variable-rate IV insulin infusion (VRIII) for major surgery. Monitor capillary glucose hourly during surgery. Avoid metformin if eGFR <30 mL/min or contrast study.

Common Traps in Endocrinology & Diabetes Questions

• Confusing DKA with HHS: HHS presents with glucose >30 mmol/L, no significant ketosis, pH >7.3, and severe dehydration—management is aggressive IV fluids, NOT high-dose insulin.
• Assuming a low TSH always means hyperthyroidism in hospitalised patients; sick euthyroid syndrome (non-thyroidal illness) can cause low TSH with low FT4 and FT3.
• Forgetting to check serum potassium before giving insulin in DKA; insulin drives potassium into cells and can cause fatal hypokalaemia if K+ <3.3 mmol/L.
• Treating subclinical hypothyroidism (TSH 4-10 mIU/L, normal FT4) with levothyroxine in all patients; NICE recommends treatment only if TSH >10 mIU/L or if symptomatic, pregnant, or trying to conceive.
• Missing Addisonian crisis because hyponatraemia and hyperkalaemia are attributed to diuretics or sepsis; always consider in unexplained shock or pigmentation.
• Giving oral glucose to an unconscious hypoglycaemic patient due to aspiration risk; must use IM glucagon or IV glucose.

How to Revise Endocrinology & Diabetes for the PLAB 1

For PLAB 1, prioritise acute endocrine emergencies (DKA, hypoglycaemia, Addisonian crisis, thyroid storm) and their stepwise management algorithms. Focus on diagnostic thresholds (HbA1c, TSH, cortisol cut-offs) and first-line drug choices (metformin, levothyroxine, bisphosphonates). Questions often present as clinical vignettes asking for the next best step (e.g., 'What is the most appropriate initial action?') or interpretation of lab results. Practise recognising red flags: weight loss with polyuria (new diabetes), palpitations with tremor (hyperthyroidism), or hypotension with hyperpigmentation (adrenal insufficiency). Also, understand DVLA rules for diabetes and sick day rules for adrenal insufficiency. Review NICE guidelines for type 1/2 diabetes, thyroid disease, and osteoporosis—especially monitoring intervals and referral criteria. Do not spend time on rare syndromes; PLAB 1 tests common, guideline-driven management.

Practise it: MedLumen has 50 Endocrinology & Diabetes questions for the PLAB 1, each with a full explanation and references.