Thyroid Disorders — Written Clinical Reasoning

SAQ 1 — Graves Disease with Atrial Fibrillation and Orbitopathy (20 marks, 30 minutes)

Prompt: Outline your integrated assessment, the investigations you would order, your immediate and definitive management plan addressing each problem, and the shared decision-making framework. Justify each decision with reference to evidence. [1]

Model Answer

Problem list (4 marks): [1]

1. Biochemically overt thyrotoxicosis — suppressed TSH with markedly elevated free T4 and free T3; the cause is almost certainly Graves disease given the diffuse smooth goitre with bruit and the orbitopathy.
2. Graves orbitopathy (moderate-severe, active) — bilateral proptosis, chemosis and diplopia on lateral gaze; this is the most important determinant of the definitive-treatment choice because radioactive iodine worsens active eye disease.
3. Atrial fibrillation with rapid ventricular response — a thyrotoxic complication with a significant thromboembolic risk that needs anticoagulation assessed and rate control.
4. High sympathetic drive / hypermetabolic state — palpitations, tremor, weight loss, heat intolerance; needs symptomatic control.
5. Modifiable risk factor for orbitopathy — she is a current smoker, which worsens Graves orbitopathy and reduces treatment response. [1]

Step 1 — Confirm the cause and complete the workup (3 marks): [1]

The clinical picture (diffuse goitre with bruit, active orbitopathy) is diagnostic of Graves disease. The first-line cause-discriminating test is serum TSH receptor antibody (TRAb) — a positive result confirms Graves without requiring a radioactive iodine uptake scan [1]. I would send TRAb, anti-TPO, FBC, LFTs and a baseline bone profile (she is perimenopausal and at osteoporotic risk from thyrotoxicosis). I would organise thyroid ultrasound to characterise the goitre and exclude coexisting nodules. I would perform a low-dose CT or MRI of the orbits to grade the orbitopathy and assess the extraocular muscles and optic nerve. I would not order a radioactive iodine uptake scan unless the TRAb were negative, because the orbitopathy already confirms Graves and the scan adds nothing that changes management.

Step 2 — Immediate symptomatic control (3 marks): [1]

• Beta-blockade — propranolol 40 mg three times daily. This controls the sympathetic symptoms (palpitations, tremor, anxiety) and, at this dose, also inhibits peripheral T4-to-T3 conversion. I would avoid it if she developed asthma or decompensated heart failure (esmolol infusion in a monitored setting would be the alternative).
• Atrial fibrillation rate control — the beta-blocker will control rate; if not adequate, add a rate-limiting calcium channel blocker (diltiazem) cautiously.
• Anticoagulation — assess her thromboembolic risk with CHA2DS2-VASc. Thyrotoxic atrial fibrillation carries a higher thromboembolic risk than non-thyrotoxic AF, so I would anticoagulate with a direct oral anticoagulant (apixaban or rivaroxaban) unless contraindicated, until she has been biochemically euthyroid for several months and the AF has reverted (or been cardioverted). [1]

Step 3 — Antithyroid drug therapy to render her euthyroid (3 marks): [1]

I would start carbimazole 30 mg daily using a titration regimen, rechecking thyroid function at 4 to 6 weeks and titrating down toward a maintenance dose of 5 to 10 mg daily once euthyroid. I would counsel her explicitly in writing on agranulocytosis: she must stop the drug and present urgently with fever, sore throat or mouth ulceration for a full blood count, particularly in the first three months. I would warn about rash, hepatic dysfunction and the small risk of pregnancy teratogenicity. I would check FBC and LFTs at baseline. A block-replace regimen (carbimazole 40 mg plus levothyroxine 100 micrograms) is a reasonable alternative if frequent titration is impractical, with comparable remission rates [1].

Step 4 — Definitive treatment, shared decision-making (4 marks): [1]

This is the crux. Three options — antithyroid drugs, radioactive iodine, surgery — are roughly equivalent in outcome, and the choice depends on her context: [1]

• Antithyroid drugs for 12 to 18 months aiming for remission: this is a reasonable first choice because she has active Graves orbitopathy (radioiodine would worsen it), she is perimenopausal (avoiding definitive hypothyroidism is reasonable), and her AF should revert once euthyroid. Remission rate 40 to 50%; relapse 50 to 60% on stopping.
• Radioactive iodine: relatively contraindicated here because she has active moderate-severe orbitopathy, which radioiodine worsens in 15% within the first year. If radioiodine were chosen, she would need prophylactic oral prednisolone (0.3 to 0.5 mg/kg/day tapering over three months) and smoking cessation first. Radioiodine is also contraindicated in pregnancy, which she should avoid for 6 to 12 months afterwards.
• Total thyroidectomy: preferred if she has a very large goitre, pressure symptoms, or a coexisting suspicious nodule, or if she prefers surgical certainty. She would need to be rendered euthyroid first and given Lugol's iodine for 10 days pre-operatively. [1]

Given her active orbitopathy and smoking history, my recommendation would be antithyroid drugs first-line with the goal of remission, combined with urgent smoking cessation and aggressive treatment of the orbitopathy, reserving surgery or radioiodine for relapse or poor tolerance. I would present all three options honestly, document her preference, and review at intervals [1].

Step 5 — Graves orbitopathy management (2 marks): [1]

She has moderate-severe active disease (proptosis, chemosis, diplopia — clinical activity score likely at least 3 out of 7). Management per the 2016 EUGOGO guidelines: smoking cessation is non-negotiable — it is the strongest modifiable risk factor and reduces treatment response. For moderate-severe active disease, first-line is intravenous methylprednisolone (cumulative dose 4.5 g over 12 weeks, e.g. 500 mg weekly) [4]. I would refer urgently to a combined endocrine-ophthalmology clinic. I would specifically assess for sight-threatening disease — optic nerve compression (reduced visual acuity, colour desaturation, relative afferent pupillary defect) or corneal breakdown — which needs urgent high-dose IV methylprednisolone (up to 1 g weekly) and urgent orbital decompression if no response.

Step 6 — Communication and follow-up (1 mark): [1]

I would frame Graves disease as an autoimmune disease that is highly treatable, with three equivalent definitive options that we would choose together. I would address her anxiety about the eye disease directly, explaining that it has a phasic course (active then inactive) and that we can treat the active phase to reduce long-term sequelae. I would discuss contraception (she must avoid pregnancy on the current plan), the risk of agranulocytosis, and the timeline to remission. I would arrange follow-up at 4 to 6 weeks with TFTs and review of the orbitopathy, and refer her to a diabetes educator equivalent (an endocrine nurse specialist), a dietitian, and an ophthalmologist. [1]

SAQ 2 — Thyroid Nodule Workup and Bethesda-Based Management (10 marks, 20 minutes)

Prompt: A 45-year-old woman is found on routine examination to have a 2.5 cm firm, non-tender thyroid nodule. She is clinically euthyroid. TSH is 2.1 mIU/L (normal). Ultrasound shows a solid, hypoechoic nodule with irregular margins, microcalcifications and a taller-than-wide shape (TI-RADS 5). Ultrasound-guided FNA is reported as 'follicular neoplasm / suspicious for a follicular neoplasm'. Outline your management approach, the Bethesda-based risk stratification, and the decision points where further investigation is required. [1]

Model Answer

Step 1 — Establish the risk profile (2 marks): [1]

The nodule has high-risk ultrasound features (hypoechoic, microcalcifications, irregular margins, taller-than-wide) scoring TI-RADS 5, which carries a malignancy risk of approximately 20% or more and mandates FNA per the 2015 ATA guidelines [3]. The normal TSH indicates a non-functioning nodule — a suppressed TSH would have suggested autonomy and prompted an uptake scan rather than FNA. There are no features of local invasion (no hoarseness, no fixation, no cervical lymphadenopathy described), but I would examine carefully for these and for a retrosternal component.

Step 2 — Apply the Bethesda System (3 marks): [1]

The cytology 'follicular neoplasm / suspicious for a follicular neoplasm' is Bethesda category IV, with an implied risk of malignancy of approximately 25 to 40% [6]. The defining feature is that follicular carcinoma cannot be distinguished from a benign follicular adenoma on cytology — the diagnosis requires histological demonstration of capsular or vascular invasion. Bethesda IV therefore mandates surgical histology, not surveillance.

The full Bethesda framework for context: [1]

Step 3 — Management decision (3 marks): [1]

The standard management for Bethesda IV is a diagnostic lobectomy (hemithyroidectomy). If histology confirms a follicular adenoma (benign), the lobectomy is curative and she needs no further surgery. If histology confirms follicular carcinoma, she undergoes completion thyroidectomy, followed by radioiodine ablation and TSH suppression. I would discuss the option of molecular testing (such as Afirma or Thyroseq) on the FNA sample — these can re-stratify risk and allow some patients to avoid surgery — but molecular testing is an adjunct, not a replacement, for the surgical decision in most cases, and lobectomy remains the default [3].

Step 4 — Pre-operative workup and counselling (2 marks): [1]

Before surgery: check vocal cord function (often asymptomatic with recurrent laryngeal nerve compression), calcium and PTH (baseline for post-operative hypoparathyroidism assessment), and arrange a neck ultrasound to exclude abnormal cervical lymph nodes. The surgical risks to discuss: recurrent laryngeal nerve injury (1 to 2% permanent hoarseness), hypoparathyroidism (transient 10 to 20%, permanent 1 to 5%), haematoma (airway emergency), and the likelihood of needing lifelong levothyroxine if completion thyroidectomy is required. [1]

Step 5 — The principle: Bethesda IV is the zone where surgery is required for diagnosis, not just for treatment — no imaging or cytology can reliably distinguish a benign follicular adenoma from a follicular carcinoma pre-operatively. The diagnostic lobectomy is both the diagnostic and (for benign disease) the therapeutic procedure. [1]