Management of Hypothyroidism and Hyperthyroidism
HYPOTHYROIDISM MANAGEMENT
Diagnosis and Initial Assessment
Diagnose hypothyroidism by measuring TSH first, followed by free T4 to distinguish overt (low free T4) from subclinical (normal free T4) disease. 1
- TSH >98% sensitive and >92% specific for detecting thyroid dysfunction 1
- Overt hypothyroidism: elevated TSH + low free T4 1, 2
- Subclinical hypothyroidism: elevated TSH + normal free T4 1, 3
- Confirm with repeat testing after 3-6 weeks, as 30-60% of elevated TSH values normalize spontaneously 1
Before initiating levothyroxine, always rule out adrenal insufficiency—especially in suspected central hypothyroidism—because starting thyroid hormone before corticosteroids can precipitate life-threatening adrenal crisis. 1, 3
- Measure morning cortisol and ACTH if central hypothyroidism suspected 1
- Start hydrocortisone at least 1 week before levothyroxine if adrenal insufficiency confirmed 1, 4
Treatment Algorithm Based on TSH Levels
TSH >10 mIU/L (with normal free T4)
Initiate levothyroxine immediately regardless of symptoms, as this threshold carries ~5% annual risk of progression to overt hypothyroidism and is associated with cardiac dysfunction and adverse lipid profiles. 1, 3, 2
- Treatment may improve symptoms and lower LDL cholesterol 1
- Evidence quality rated as "fair" by expert panels 1
TSH 4.5-10 mIU/L (with normal free T4)
Do not routinely treat asymptomatic patients, as randomized trials show no symptomatic benefit; instead monitor TSH every 6-12 months. 1, 3
Consider treatment in specific situations:
- Symptomatic patients (fatigue, weight gain, cold intolerance, constipation) may benefit from 3-4 month trial with clear evaluation of response 1, 5
- Pregnant women or those planning pregnancy—target TSH <2.5 mIU/L in first trimester 1, 3
- Positive anti-TPO antibodies (4.3% vs 2.6% annual progression risk) 1
- Patients with goiter or infertility 1, 3
Levothyroxine Dosing Strategy
Standard Dosing (Age <70, No Cardiac Disease)
Start with full replacement dose of 1.6 mcg/kg/day for most young, healthy patients. 1, 3, 5
- Monitor TSH every 6-8 weeks during titration 1
- Target TSH 0.5-4.5 mIU/L with normal free T4 1, 3
- Adjust by 12.5-25 mcg increments based on response 1
High-Risk Patients (Age >70, Cardiac Disease, Severe Long-Standing Hypothyroidism)
Start at low dose of 25-50 mcg/day and titrate slowly by 12.5-25 mcg every 6-8 weeks to avoid unmasking cardiac ischemia or precipitating arrhythmias. 1, 3, 5, 6
- Elderly patients with coronary disease at highest risk for cardiac decompensation 1
- Use smaller increments (12.5 mcg) in very elderly or cardiac patients 1
Pregnancy Considerations
Women with pre-existing hypothyroidism should increase levothyroxine by 25-50% immediately upon pregnancy confirmation. 1
- Monitor TSH every 4 weeks until stable, then at minimum once per trimester 1
- Target TSH <2.5 mIU/L in first trimester 1
- Untreated hypothyroidism increases risk of preeclampsia, low birth weight, and neurodevelopmental deficits 1, 5
Monitoring and Long-Term Management
Recheck TSH and free T4 every 6-8 weeks after any dose adjustment until target reached, then annually once stable. 1, 3
- Free T4 helps interpret ongoing abnormal TSH during therapy 1
- TSH may take longer to normalize than free T4 1
Critical pitfall: Approximately 25% of patients are unintentionally overtreated with suppressed TSH, increasing risk for atrial fibrillation (3-5 fold), osteoporosis, fractures, and cardiovascular mortality. 1, 2, 5
Managing Overtreatment
If TSH <0.1 mIU/L: Reduce levothyroxine by 25-50 mcg immediately. 1
If TSH 0.1-0.45 mIU/L: Reduce by 12.5-25 mcg, especially in elderly or cardiac patients. 1
- Prolonged TSH suppression dramatically increases atrial fibrillation risk in elderly 1
- Postmenopausal women face accelerated bone loss and fracture risk 1
Special Populations
Patients on Immune Checkpoint Inhibitors
Consider levothyroxine even for subclinical hypothyroidism if fatigue or symptoms present, as thyroid dysfunction occurs in 6-9% with anti-PD-1/PD-L1 therapy. 1
- Continue immunotherapy in most cases 1
- Monitor TSH every 4-6 weeks for first 3 months, then every second cycle 1
Central Hypothyroidism
Always evaluate and treat adrenal insufficiency before starting levothyroxine. 1, 3
- Monitor treatment with free T4 (not TSH), targeting upper half of normal range 3
- Evaluate other pituitary hormones 3
HYPERTHYROIDISM MANAGEMENT
Initial Treatment and Symptom Control
Start beta-blockers immediately for symptomatic relief of palpitations, tremors, tachycardia, and anxiety—propranolol 60-80 mg orally every 4-6 hours is preferred. 7, 4, 8
- Target heart rate <100 bpm 4
- If beta-blockers contraindicated, use diltiazem or verapamil 4
- Beta-blockers improve cardiac symptoms rapidly while direct thyroid effects persist 7
Definitive Treatment Options
Three recognized modalities exist: antithyroid drugs, radioiodine, and surgery—no single method offers absolute cure. 8
Antithyroid Drugs (Methimazole or Propylthiouracil)
For Graves' disease, prescribe antithyroid drugs for 12-18 months to induce long-term remission. 8
- Also used short-term to render patient euthyroid before radioiodine or surgery 8
- Will not cure toxic nodular goiter 8
Radioiodine Therapy
Radioiodine is increasingly used as first-line therapy and is well tolerated, with only long-term sequela being risk of hypothyroidism. 8
- Treatment of choice for toxic nodular goiter 8
- Avoid in pregnancy, lactation, and children 8
- Avoid pregnancy for 4 months after administration 8
- May worsen Graves' ophthalmopathy—consider corticosteroid cover 8
Surgery (Subtotal or Near-Total Thyroidectomy)
Surgery has limited but specific roles: large goiter causing compressive symptoms, or when radioiodine refused. 8
- Goal is to cure pathology while leaving residual tissue for euthyroidism 8
- Rarely used in Graves' disease unless specific indications 8
Thyroid Storm (Life-Threatening Emergency)
Thyroid storm requires immediate multi-modal treatment in intensive care setting. 4
Treatment protocol:
- Propranolol 1-2 mg IV slowly every 10-15 minutes until heart rate controlled 4
- Propylthiouracil or methimazole to block thyroid hormone synthesis 4
- Potassium iodide solutions to block hormone release 4
- Dexamethasone to block peripheral conversion 4
- Aggressive IV hydration (≥2L normal saline initially) for dehydration from fever 4
- Continuous cardiac monitoring for arrhythmias, especially atrial fibrillation 4
Mortality rate up to 30% if untreated. 2
Monitoring During Treatment
For thyroiditis with thyrotoxic phase, monitor thyroid function every 2-3 weeks to detect transition to hypothyroidism. 4
- If thyrotoxic phase persists beyond 6 weeks, consider endocrinology consultation 4
- Initiate levothyroxine if hypothyroidism develops 4
Common Pitfalls to Avoid
In hypothyroidism:
- Never start levothyroxine before ruling out adrenal insufficiency in central hypothyroidism 1, 3
- Never treat based on single elevated TSH—confirm with repeat testing 1
- Never ignore suppressed TSH in treated patients—25% are unintentionally overtreated 1, 2
- Never assume hypothyroidism is permanent without reassessment—37% of subclinical cases normalize spontaneously 1
In hyperthyroidism: