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IM12.1-14 | Thyroid Dysfunction — PBL Case

CLINICAL SETTING

It is a busy Monday morning at the general medicine outpatient clinic at a Government Medical College and Hospital in Tamil Nadu. Dr Ananya, a final-year MBBS student on her medicine posting, is sitting in with Dr Suresh, the registrar. The next patient is Mrs Malathi Chandran, a 38-year-old school principal from a semi-urban town, brought in by her husband. He tells Dr Suresh: 'She has been unwell for several months, doctor. She has lost 12 kg. She is always anxious, always sweating, and she had a frightening episode last week — her heart was racing so fast she thought she was having a heart attack.' Mrs Malathi sits in the chair, visibly tremulous. She appears thin, with prominent eyes. Her hands are shaking. Her husband adds, quietly: 'She has been hiding how bad it was. She thought it would pass on its own.' Dr Ananya opens her logbook and writes: 'Possible thyroid disease? What should I look for?'

Trigger 1: History and First Examination Findings

Dr Suresh takes a structured history. Mrs Malathi confirms: palpitations for 5 months (worse on exertion and at rest), weight loss of 12 kg in 4 months despite eating more than usual, profuse sweating, intolerance to heat, loose stools 3–4 times daily, hand tremor that prevents her from writing on the blackboard, and difficulty sleeping. She also reports that her menstrual cycles stopped 2 months ago. She has no significant past medical history and takes no medications. Family history: her elder sister was treated for 'thyroid' and had her thyroid removed surgically 5 years ago. On examination: BP 148/64 mmHg (wide pulse pressure), heart rate 138/min irregular; thyroid — diffuse smooth goitre approximately 2.5× normal size, non-tender, with a soft bruit audible over both lobes; bilateral exophthalmos with lid lag; fine resting tremor of both hands; warm moist palms; mild bilateral lower limb non-pitting oedema. Dr Ananya lists the most striking findings in her logbook. Dr Suresh asks: 'Before we order any investigations — from the history and examination alone, can you construct a differential diagnosis? And which single finding most strongly points to one specific cause over all others?'

DISCUSSION POINTS

  • Construct a prioritised differential diagnosis for this presentation — what features distinguish Graves disease from toxic multinodular goitre and subacute thyroiditis?
  • Which single clinical finding in this patient most specifically implicates Graves disease, and why is it pathognomonic of this condition rather than other causes of thyrotoxicosis?
  • What is the physiological explanation for the wide pulse pressure (systolic BP elevated, diastolic low) seen in thyrotoxicosis, and what cardiac complication does the irregular heart rate suggest?
Click to reveal Trigger 2: Investigation Results and a Diagnostic Challenge (discuss previous trigger first!)

Trigger 2: Investigation Results and a Diagnostic Challenge

Blood tests are sent. The results return within 2 hours: TSH <0.01 mIU/L; FT4 72 pmol/L (normal 12–22); FT3 22 pmol/L (normal 3.5–6.5); TRAb 9.4 IU/L (normal <1.8); anti-TPO 48 IU/mL (weakly positive). CBC: Hb 11.2 g/dL, WBC 6.8 × 10^9/L (normal differential), platelets 188 × 10^9/L. ECG: ventricular rate 138/min, irregularly irregular rhythm, absent P waves, no delta waves; QRS morphology normal; no ST-T changes. Dr Suresh reviews the ECG and says: 'She is in atrial fibrillation. This changes one aspect of our immediate management.' He asks Dr Ananya: 'The TRAb is 9.4 — five times the upper limit of normal. Why does this number matter beyond confirming the diagnosis?' Dr Ananya is puzzled. Dr Suresh continues: 'This patient is not pregnant now — but if she were, what would that TRAb level mean for the fetus?'

DISCUSSION POINTS

  • Interpret the TFT pattern: classify it using the standard framework, and explain what the combination of markedly suppressed TSH, very high FT4, and high FT3 tells you about the severity of disease.
  • The ECG shows atrial fibrillation in a patient with Graves thyrotoxicosis. What is the initial management priority — rate control, rhythm control, or anticoagulation? Which drug for rate control and why?
  • TRAb at 9.4 IU/L (5× ULN) in a patient of reproductive age — what is the clinical significance of a very high TRAb titre with respect to future pregnancy, fetal thyroid function, and neonatal monitoring?
Click to reveal Trigger 3: Starting Treatment — and an Unexpected Complication (discuss previous trigger first!)

Trigger 3: Starting Treatment — and an Unexpected Complication

Mrs Malathi is started on carbimazole 40 mg daily and propranolol 40 mg three times daily for rate control. She is counselled and discharged with a follow-up in 6 weeks. Three weeks later she returns as an emergency: fever 39.2°C, severe sore throat, and painful mouth ulcers since 2 days. Her husband is alarmed. A repeat CBC is sent urgently: Hb 10.8 g/dL, WBC 1.4 × 10^9/L, absolute neutrophil count (ANC) 0.38 × 10^9/L. Dr Suresh looks at the result and says to Dr Ananya: 'This is the adverse effect I counselled her about at the first visit. Do you recall? What must we do right now?' He adds: 'Before you answer — tell me what you should NOT do, which is just as important as what you should do.'

DISCUSSION POINTS

  • What is the diagnosis, and what is the immediate management? State in order the actions that must be taken in the next 60 minutes.
  • What must NOT be done — specifically regarding continuation of the offending drug, switching to another thionamide, or self-managing at home — and why?
  • How could this complication have been anticipated or detected earlier? Design the counselling checklist that every patient started on a thionamide should receive at the time of prescription.
Click to reveal Trigger 4: Definitive Therapy Decision and a Deteriorating Inpatient (discuss previous trigger first!)

Trigger 4: Definitive Therapy Decision and a Deteriorating Inpatient

Mrs Malathi recovers from agranulocytosis over 10 days with IV antibiotics and G-CSF. She is discharged on no antithyroid drug, with a plan to discuss definitive therapy. At the outpatient review, Dr Suresh presents three options: carbimazole re-challenge (with close monitoring), radioiodine, or thyroidectomy. During the discussion, Mrs Malathi's husband receives a call and urgently tells the doctor: 'There is a patient outside in the waiting room — another of your patients — who has been brought by the family. She looks very unwell.' The team steps out: they find Mrs Pushpa Venkatesan, a 62-year-old woman who was being treated for uncontrolled thyrotoxicosis. She is confused, febrile at 40.1°C, has a heart rate of 162/min in atrial fibrillation, is agitated and has vomited twice. The Burch-Wartofsky Point Scale is calculated at 60. Her family says she developed the acute deterioration 6 hours after a contrast CT scan performed for an abdominal complaint.

DISCUSSION POINTS

  • For Mrs Malathi: evaluate the three definitive therapy options — carbimazole, radioiodine, surgery — weighing indications, contraindications, and which is preferred given her history of agranulocytosis and high TRAb.
  • For Mrs Pushpa: what is the diagnosis, what is the Burch-Wartofsky score interpretation, and what is the correct multi-drug treatment sequence? Specifically, why must PTU be given BEFORE iodine and not the other way around?
  • What precipitant caused Mrs Pushpa's thyroid storm, and what is the mechanism? Name three other common precipitants of thyroid storm and describe how each triggers the decompensation.

Group Task Assignments

  • Using Mrs Malathi's case, construct a one-page patient information sheet (in plain language, appropriate for a semi-literate patient) explaining: (a) what Graves disease is, (b) why she must take her tablets daily, (c) the one symptom that requires her to stop the tablet immediately and attend emergency — and what NOT to do (self-medicate, reduce dose, switch brands without advice).
  • Review the Burch-Wartofsky Point Scale: using Mrs Pushpa's documented features (temperature 40.1°C, heart rate 162/min in AF, confusion, vomiting, precipitant = iodine contrast), calculate her score step by step and justify each sub-score. Identify which features contributed the most points.
  • Design a thyroid storm treatment protocol card for a district hospital with limited resources — covering the first 6 hours. Include drug name, dose, route, timing sequence, and the rationale for the specific sequence (especially PTU before iodine before propranolol before hydrocortisone ordering logic).
  • Debate the definitive therapy choices for Graves disease in the Indian context: which option (carbimazole long-term, radioiodine, surgery) is most feasible, most cost-effective, and most appropriate for a school principal of reproductive age with high TRAb and a history of agranulocytosis? Consider patient preference, access, and the risk of hypothyroidism as an outcome.

Learning Issues

Research these questions and bring your findings to the discussion.

  1. [IM12.1] What is the pathogenesis of Graves disease — specifically, what is the role of TSH receptor antibodies in driving thyroid hormone overproduction and causing extrathyroidal manifestations such as ophthalmopathy and pretibial myxoedema?
  2. [IM12.10] How do you classify and interpret the TFT pattern of overt hyperthyroidism (suppressed TSH + elevated FT4 + elevated FT3) versus T3 thyrotoxicosis, and what additional test must always be ordered when TSH is suppressed but FT4 is normal?
  3. [IM12.9] What are the ECG findings in thyrotoxicosis — specifically atrial fibrillation — and what is the management of AF in hyperthyroidism with regard to rate control, rhythm control, and the threshold for anticoagulation?
  4. [IM12.12] What is the pharmacology, mechanism, adverse effect profile, and patient counselling requirements for carbimazole — including the life-threatening adverse effect of agranulocytosis and the absolute contraindication rule in the first trimester of pregnancy?
  5. [IM12.14] What are the indications for the three definitive treatment modalities (thionamides, radioiodine, thyroidectomy) in Graves disease and toxic nodular goitre, and what is the full multi-drug treatment protocol and sequence for thyroid storm (Burch-Wartofsky criteria, PTU → iodine → propranolol → hydrocortisone)?