What is the treatment for a patient with hypothyroidism, indicated by low T3 (Triiodothyronine) and T4 (Thyroxine) levels, and elevated TSH (Thyroid-Stimulating Hormone) level?

Treatment for Overt Primary Hypothyroidism

Initiate levothyroxine immediately at a weight-based dose of approximately 1.6 mcg/kg/day for adults under 70 years without cardiac disease, as your laboratory values (free T3 <1, free T4 <1.17, TSH 37.4) indicate severe overt primary hypothyroidism requiring urgent treatment to prevent cardiovascular dysfunction, metabolic complications, and further quality of life deterioration. 1

Immediate Treatment Initiation

• Start levothyroxine without delay when both TSH is markedly elevated (37.4 mIU/L) AND free T4 is below the reference range, as this represents overt hypothyroidism with significant risk of cardiovascular dysfunction, adverse lipid profiles, and quality of life deterioration 1
• For most adults under 70 years without cardiac disease or multiple comorbidities, the full replacement dose of approximately 1.6 mcg/kg/day can be initiated immediately 1, 2
• This typically translates to 100-150 mcg daily for most women and 125-175 mcg daily for most men 3

Critical Safety Considerations Before Starting Treatment

Before initiating levothyroxine, you must rule out concurrent adrenal insufficiency, as starting thyroid hormone before corticosteroids can precipitate life-threatening adrenal crisis 1

• If central hypothyroidism or hypophysitis is suspected (though your elevated TSH indicates primary hypothyroidism), always start physiologic dose steroids 1 week prior to thyroid hormone replacement 1
• In patients with suspected concurrent adrenal insufficiency, start corticosteroids several days before initiating or increasing thyroid hormone 1

Modified Dosing for High-Risk Patients

If you are over 70 years old OR have underlying cardiac disease (coronary artery disease, heart failure, arrhythmias), start with a lower dose of 25-50 mcg/day and titrate gradually to avoid exacerbating cardiac symptoms or precipitating cardiac decompensation 1, 2

• Elderly patients with coronary disease are at increased risk of cardiac decompensation, angina, or arrhythmias even with therapeutic levothyroxine doses 1
• For these high-risk patients, titrate the dosage every 6-8 weeks as needed until euthyroid, using smaller increments (12.5 mcg) 1

Administration Instructions

• Administer levothyroxine as a single daily dose on an empty stomach, one-half to one hour before breakfast with a full glass of water 2
• Take at least 4 hours before or after drugs that interfere with absorption (calcium, iron, bile acid sequestrants, proton pump inhibitors, antacids) 2
• Avoid foods that decrease absorption, including soybean flour, cottonseed meal, walnuts, dietary fiber, and grapefruit juice 2

Monitoring and Dose Titration

Recheck TSH and free T4 in 6-8 weeks after starting treatment, as this represents the time needed to reach steady state 1

• The peak therapeutic effect of a given dose may not be attained for 4-6 weeks 2
• Target TSH within the reference range (0.5-4.5 mIU/L) with normal free T4 levels 1
• For dose adjustments, increase by 12.5-25 mcg increments based on your current dose and clinical characteristics 1
• Once adequately treated with a stable dose, repeat TSH testing every 6-12 months or if symptoms change 1

Expected Outcomes and Symptom Resolution

• Levothyroxine replacement effectively eradicates symptoms of hypothyroidism and normalizes thyroid hormone values in the majority of patients 3
• Treatment prevents complications including cardiovascular dysfunction (delayed relaxation, abnormal cardiac output), adverse lipid profiles, and quality of life deterioration 1
• Complete remission of symptoms usually occurs when thyroid hormone concentrations return to normal 3

Common Pitfalls to Avoid

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

• Avoid excessive dose increases that could lead to iatrogenic hyperthyroidism 1
• Do not adjust doses too frequently before reaching steady state—wait 6-8 weeks between adjustments 1
• Never assume hypothyroidism is permanent without reassessment; consider transient thyroiditis in recovery phase where TSH can be elevated temporarily 1
• TSH suppression (<0.1 mIU/L) significantly increases risk of atrial fibrillation (5-fold in individuals ≥45 years) and fractures, particularly in women >65 years 1

Long-Term Management Considerations

• Ensure adequate calcium (1200 mg/day) and vitamin D (1000 units/day) intake to prevent bone demineralization, especially if TSH becomes chronically suppressed 1
• If you become pregnant, increase your weekly levothyroxine dosage by 30% (take one extra dose twice per week), followed by monthly evaluation 4
• Levothyroxine requirements may increase during pregnancy by 25-50% above pre-pregnancy doses for proper fetal neurologic development 1