Disorders of Thyroid Hormones – Clinical Scenarios with Lab Data
You will be presented with 8 clinical scenarios of children with suspected thyroid disorders.
For each, interpret the lab data and provide: 1) Diagnosis, 2) Any other test, 3) What to do next, 4) Follow-up plan.
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Primary hypothyroidism: ↑TSH, ↓T4Graves: ↓TSH, ↑T4, TRAb+Subacute thyroiditis: ↓TSH, ↑T4, ↓RAIUHashimoto: ↑TPO, may be euthyroid
Case 1
A newborn screening shows elevated TSH. The infant is asymptomatic on exam.
Serum TSH
85 mIU/L (elevated)
Free T4
0.5 ng/dL (low)
Total T4
2.8 mcg/dL (low)
Thyroglobulin
Low
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Congenital hypothyroidism – likely thyroid dysgenesis (low thyroglobulin suggests agenesis).
• Any other test: Thyroid ultrasound or 123I scintigraphy to determine if thyroid is absent, ectopic, or hypoplastic.
• What to do next: Start levothyroxine 10-15 mcg/kg/day immediately. Do NOT wait for imaging results.
• Follow-up plan: Monitor TSH and free T4 every 1-2 months in first 6 months, then every 2-4 months. Goal TSH 0.5-5.0 mIU/L, free T4 in upper half of normal. Lifelong therapy.
Case 2
A 10-year-old girl with fatigue, and weight gain. She has a firm, rubbery, non-tender goiter.
TSH
45 mIU/L (elevated)
Free T4
0.6 ng/dL (low)
Anti-TPO Antibodies
Positive (>1000 IU/mL)
Anti-Tg Antibodies
Positive
Blood Pressure
110/70 mm Hg
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Hashimoto thyroiditis (autoimmune) with overt primary hypothyroidism.
• Any other test: TSH receptor antibodies (if hyperthyroid symptoms), screen for celiac disease (TTG IgA), type 1 diabetes (HbA1c), and adrenal insufficiency (if symptoms).
• What to do next: Start levothyroxine 1.6-2 mcg/kg/day (approximately 50-75 mcg/day for a 30 kg child). Obtain bone age X-ray if growth failure.
• Follow-up plan: Check TSH and free T4 in 4-6 weeks. Once stable, monitor TSH every 3-6 months. Goal TSH 0.5-5.0 mIU/L. Annual thyroid function tests.
Case 3
A 14-year-old girl with palpitations, weight loss, heat intolerance, and a diffuse goiter.
TSH
<0.01 mIU/L (suppressed)
Free T4
3.8 ng/dL (elevated)
Free T3
12 pg/mL (elevated)
TSH Receptor Antibodies (TRAb)
Positive (8 IU/L)
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Graves disease (autoimmune hyperthyroidism) – TRAb positive, diffuse goiter, suppressed TSH, elevated T4/T3.
• Any other test: Thyroid ultrasound to assess goiter/vascularity; baseline CBC, LFTs before starting methimazole; consider ophthalmology consult.
• What to do next: Start methimazole 0.5-1 mg/kg/day (max 40 mg/day) divided BID, and propranolol 1-2 mg/kg/day for tachycardia/tremor.
• Follow-up plan: Check free T4 and TSH every 4-6 weeks. Adjust methimazole to lowest effective dose. Monitor CBC for agranulocytosis, LFTs. Methimazole course 2-4 years; remission rate 25-50%.
Case 4
A 12-year-old with a painful, tender goiter, fever, and recent viral URI.
TSH
0.02 mIU/L (suppressed)
Free T4
3.2 ng/dL (elevated)
ESR
85 mm/hr (elevated)
TSH Receptor Antibodies (TRAb)
Negative
Radioiodine Uptake (RAIU)
Very low (<5%)
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Subacute (de Quervain) thyroiditis – post-viral, painful goiter, elevated ESR, low RAIU (no increased hormone synthesis).
• Any other test: Thyroid ultrasound to exclude abscess/suppurative thyroiditis; TPO antibodies (may be negative).
• What to do next: NSAIDs (ibuprofen) for pain. Prednisone 20-40 mg/day for severe pain. Propranolol for thyrotoxic symptoms. NO antithyroid drugs (methimazole ineffective).
• Follow-up plan: Check TSH and free T4 every 4-6 weeks. May enter hypothyroid phase (treat with levothyroxine if symptomatic). Most recover to euthyroid within months.
Case 5
A 15-year-old boy with a palpable thyroid nodule discovered on routine exam. He is asymptomatic.
TSH
2.5 mIU/L (normal)
Free T4
1.2 ng/dL (normal)
Thyroid Ultrasound
1.8 cm solid nodule, hypoechoic, microcalcifications, irregular margins
Cervical Lymph Nodes
None palpable
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Thyroid nodule with suspicious ultrasound features (hypoechoic, microcalcifications, irregular margins). Risk of malignancy 20-25% in children.
• Any other test: Fine needle aspiration (FNA) of the nodule under ultrasound guidance. Bethesda classification determines management.
• What to do next: Perform FNA. If Bethesda II (benign) → observe. If Bethesda V/VI (suspicious/malignant) → total thyroidectomy + central neck dissection.
• Follow-up plan: Benign: repeat ultrasound in 6-12 months, then annually. If malignant: total thyroidectomy + central neck dissection; post-op levothyroxine suppression. Surveillance with thyroglobulin and ultrasound.
Case 6
A 16-year-old girl with weight gain, fatigue, and constipation. She has a firm goiter.
TSH
8.5 mIU/L (elevated)
Free T4
1.0 ng/dL (normal)
Anti-TPO Antibodies
Positive
Anti-Tg Antibodies
Positive
Symptoms
Mild fatigue, weight gain
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Subclinical hypothyroidism due to Hashimoto thyroiditis (autoimmune). TSH >7.5 with normal free T4, positive TPO antibodies.
• Any other test: Screen for associated autoimmune conditions: celiac disease (TTG IgA), type 1 diabetes (HbA1c), Addison disease if symptoms.
• What to do next: Start levothyroxine 25-50 mcg/day (or 1.6 mcg/kg) given TSH >7.5 and/or symptoms. If TSH 4.5-7.5 with TPO positive, consider treatment.
• Follow-up plan: Check TSH and free T4 in 6 weeks, then every 3-6 months. Goal TSH 0.5-5.0 mIU/L. If untreated, monitor TSH annually.
Case 7
A neonate born to a mother with Graves disease. The infant is tachycardic, irritable, and has a goiter.
TSH
<0.01 mIU/L (suppressed)
Free T4
4.0 ng/dL (elevated)
Free T3
14 pg/mL (elevated)
Maternal TRAb
Positive (high titer)
Heart Rate
180 bpm
Birth Weight
2.0 kg (IUGR)
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Neonatal Graves disease – transient hyperthyroidism due to maternal TSH receptor-stimulating antibodies (TRAb) crossing placenta.
• Any other test: Confirm maternal and neonatal TRAb levels. Thyroid ultrasound to assess goiter. Cardiac evaluation for tachycardia/heart failure.
• What to do next: Start methimazole 0.5-1 mg/kg/day (divided q8h) and propranolol 0.5-1 mg/kg/day for tachycardia. Monitor for heart failure, feeding difficulties.
• Follow-up plan: Check TSH, free T4 daily initially. Wean methimazole as TRAb clears (typically 3-6 months). Most infants become euthyroid; rarely requires long-term therapy.
Case 8
A 13-year-old girl with a multinodular goiter. She has a family history of thyroid nodules.
TSH
0.02 mIU/L (suppressed)
Free T4
2.8 ng/dL (elevated)
Free T3
8.5 pg/mL (elevated)
Thyroid Ultrasound
Multinodular goiter, dominant nodule 2.5 cm
TSH Receptor Antibodies (TRAb)
Negative
Radioiodine Uptake (RAIU)
High with diffuse uptake
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Toxic multinodular goiter (or Graves disease with negative TRAb – rare).
• Any other test: Thyroid scan (123I or 99mTc) to identify hyperfunctioning nodules. FNA of dominant nodule if suspicious features. Family history for familial non-autoimmune hyperthyroidism (TSHR mutations).
• What to do next: Start methimazole 0.5-1 mg/kg/day to control hyperthyroidism. Beta-blocker for symptoms. For definitive therapy: radioactive iodine (RAI) or thyroidectomy.
• Follow-up plan: Monitor TSH, free T4. If RAI or surgery, lifelong levothyroxine replacement. If continued methimazole, monitor for remission.
🎯 Examiner Scoring Checklist
• Correctly identifies primary vs central thyroid disorders
• Recognizes congenital hypothyroidism and initiates treatment promptly
• Distinguishes Graves disease from subacute thyroiditis
• Identifies thyroid nodules and recommends appropriate workup
• Understands monitoring and follow-up protocols
📌 Key Thyroid Hormone Interpretation:
• Primary hypothyroidism: ↑TSH, ↓T4 (Hashimoto, dysgenesis)
• Central hypothyroidism: ↓TSH, ↓T4 (pituitary/hypothalamic)
• Graves disease: ↓TSH, ↑T4, TRAb+
• Subacute thyroiditis: ↓TSH, ↑T4, ↓RAIU
• Thyroid nodule: Normal TSH, US-guided FNA if >1 cm with suspicious features
📋 Mock Test Feedback
💡 Examiner's note: Compare your answers with model answers. In real TOACS, you would discuss these with the examiner.