Treatment for Hypothyroidism
Levothyroxine monotherapy is the first-line treatment for hypothyroidism, with dosing tailored to patient age, cardiac status, and severity of disease. 1, 2, 3
Initial Treatment Selection
Levothyroxine (synthetic T4) is the standard of care for all forms of hypothyroidism, whether overt (elevated TSH with low free T4) or subclinical (elevated TSH with normal free T4). 1, 4, 5
The medication is chemically identical to endogenous thyroxine and has been the mainstay of treatment for decades, with proven efficacy in normalizing thyroid function and preventing complications. 2, 4
Starting Dose Strategy
For Younger Patients Without Cardiac Disease
Start with full replacement dose of approximately 1.6 mcg/kg/day for patients under 70 years without cardiac disease or multiple comorbidities. 1
This approach rapidly normalizes thyroid function and prevents complications such as cardiovascular dysfunction, adverse lipid profiles, and quality of life deterioration. 1
For Elderly or Cardiac Patients
Start with 25-50 mcg/day for patients over 70 years or those with cardiac disease, atrial fibrillation, or coronary artery disease. 1, 2, 5
Elderly patients with coronary disease are at increased risk of cardiac decompensation, angina, or arrhythmias even with therapeutic levothyroxine doses, as the medication can unmask or worsen cardiac ischemia. 1
Titrate gradually with smaller increments (12.5 mcg) to avoid cardiac complications. 1
Monitoring and Dose Adjustment
Recheck TSH and free T4 every 6-8 weeks while titrating hormone replacement, as this represents the time needed to reach steady state. 1, 3
Target TSH range is 0.5-4.5 mIU/L with normal free T4 levels for primary hypothyroidism. 1, 4, 5
Adjust dose by 12.5-25 mcg increments based on patient's current dose and clinical characteristics—use smaller increments (12.5 mcg) for elderly or cardiac patients. 1
Once adequately treated, monitor TSH annually or sooner if symptoms change. 1, 3
Critical Safety Considerations
Rule Out Adrenal Insufficiency First
Never start levothyroxine before ruling out concurrent adrenal insufficiency, especially in patients with suspected central hypothyroidism or hypophysitis, as this can precipitate life-threatening adrenal crisis. 1
In patients with suspected pituitary or hypothalamic disease, always start physiologic dose corticosteroids 1 week prior to thyroid hormone replacement. 1
Pregnancy Considerations
Levothyroxine should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated. 2
Pregnancy may increase levothyroxine requirements by 25-50%, necessitating proactive dose adjustments for proper fetal neurologic development. 1, 2
Untreated maternal hypothyroidism is associated with spontaneous abortion, gestational hypertension, pre-eclampsia, stillbirth, premature delivery, and adverse effects on fetal neurocognitive development. 1, 2
Monitor TSH during pregnancy and adjust dosage accordingly; return to pre-pregnancy dose immediately after delivery. 2
Treatment Thresholds Based on TSH Levels
TSH >10 mIU/L
Initiate levothyroxine therapy regardless of symptoms, as this level carries approximately 5% annual risk of progression to overt hypothyroidism and is associated with increased cardiovascular risk. 1, 5
Treatment may improve symptoms and lower LDL cholesterol, though evidence for mortality benefit is limited. 1
TSH 4.5-10 mIU/L (Subclinical Hypothyroidism)
Routine levothyroxine treatment is not recommended for asymptomatic patients; instead monitor thyroid function tests every 6-12 months. 1, 5
Consider treatment in specific situations: symptomatic patients with fatigue or other hypothyroid complaints, pregnant women or those planning pregnancy, patients with positive anti-TPO antibodies (4.3% annual progression risk vs 2.6% in antibody-negative individuals), or patients with infertility or goiter. 1, 5
A 3-4 month trial of levothyroxine with clear evaluation of benefit is reasonable for symptomatic patients. 1
Common Pitfalls to Avoid
Overtreatment Risks
Approximately 25% of patients on levothyroxine are unintentionally maintained on doses sufficient to fully suppress TSH, increasing risks for atrial fibrillation, osteoporosis, fractures, abnormal cardiac output, and ventricular hypertrophy. 1, 3
Overtreatment occurs in 14-21% of treated patients and is particularly dangerous in elderly patients and postmenopausal women. 1
**TSH suppression (<0.1 mIU/L) significantly increases risk** for atrial fibrillation (5-fold increased risk in individuals ≥45 years), fractures (particularly hip and spine in women >65 years), cardiovascular mortality, and bone demineralization. 1
Confirm Diagnosis Before Treatment
Do not treat based on a single elevated TSH value, as 30-60% of elevated TSH levels normalize spontaneously on repeat testing. 1, 5
Confirm elevated TSH with repeat testing after 3-6 weeks before initiating treatment, as transient elevations are common during recovery from thyroiditis or acute illness. 1
Medication Administration
- Levothyroxine should be taken consistently, preferably on an empty stomach, as absorption can be affected by food, certain medications (calcium, iron supplements, proton pump inhibitors), and gastrointestinal disorders. 4
Alternative Therapies
Combination therapy with levothyroxine plus liothyronine (T3) is not routinely recommended as standard treatment. 6
While some studies showed patient preference for combination therapy and potential benefits on mood and quality of life, these benefits must be balanced against the possibility of adverse events from liothyronine addition. 6
Until clear advantages are demonstrated, levothyroxine monotherapy should remain the treatment of choice. 6
Long-Term Management
Hypothyroidism typically requires lifelong treatment with levothyroxine to maintain normal thyroid function and prevent complications. 7, 4
With appropriate treatment and monitoring, symptoms can be effectively managed and most patients can lead normal, healthy lives. 7
Lifestyle modifications including healthy diet and regular exercise can help manage symptoms and improve quality of life. 7