What is the best course of action for a patient with primary hypothyroidism, taking levothyroxine (T4) 75mcg every other day, with a high Thyroid-Stimulating Hormone (TSH) level of 12.0, normal T4, mildly elevated liver enzymes, normal kidney function, normal blood counts, and normal lipid profiles, who recently changed to levothyroxine 88mcg once daily?

Increase levothyroxine to 88mcg daily immediately—the patient was severely underdosed at 75mcg every other day, and the TSH of 12.0 confirms inadequate treatment requiring prompt correction.

Assessment of Current Situation

You made the right decision. The patient was taking levothyroxine 75mcg every other day (equivalent to only ~37.5mcg daily average), which is grossly insufficient for treating primary hypothyroidism 1, 2. The TSH of 12.0 mIU/L with normal T4 represents overt primary hypothyroidism requiring immediate treatment, not a situation where you "jumped the gun" 1.

Why the Every-Other-Day Dosing Was Problematic

• Levothyroxine has a long half-life and should be administered as a single daily dose to maintain stable thyroid hormone levels 3
• Every-other-day dosing creates unnecessary fluctuations in serum levels and makes dose titration extremely difficult 3
• The average daily dose of ~37.5mcg is far below the typical replacement requirement of 1.6 mcg/kg/day for most adults 1, 2, 3

Rationale for 88mcg Daily Dosing

The 88mcg daily dose is appropriate and evidence-based:

• For TSH >10 mIU/L, levothyroxine therapy should be initiated or increased regardless of symptoms, as this level carries approximately 5% annual risk of progression to more severe hypothyroidism and is associated with cardiovascular dysfunction 1
• The recommended dose adjustment increment is 12.5-25 mcg based on current dose 1, 2
• Moving from 75mcg every other day (~37.5mcg daily average) to 88mcg daily represents a reasonable increase that will normalize thyroid function without risking overtreatment 1, 2

Monitoring Protocol

Follow this specific timeline:

• Recheck TSH and free T4 in 6-8 weeks after starting 88mcg daily, as this represents the time needed to reach steady state 1, 2
• Target TSH should be 0.5-4.5 mIU/L with normal free T4 levels 1, 2
• If TSH remains elevated after 6-8 weeks, increase by another 12.5-25 mcg increment 1, 2
• Once TSH normalizes, monitor every 6-12 months or sooner if symptoms change 1, 2

Addressing the Mildly Elevated Liver Enzymes

Your plan to recheck in 3 months is appropriate:

• Hypothyroidism itself can cause mild liver enzyme elevations through delayed hepatic metabolism 1
• The AST 45 and ALT 33 are only mildly elevated and likely multifactorial (statin, possible fatty liver, uncontrolled thyroid) 1
• Optimizing thyroid function first before attributing liver enzyme elevation to other causes is the correct approach 1
• Rechecking after thyroid optimization (3 months) will help determine if the elevation was thyroid-related 1

Critical Administration Instructions

Ensure the patient understands proper levothyroxine administration:

• Take on an empty stomach, 30-60 minutes before breakfast with a full glass of water 3
• Administer at least 4 hours before or after iron, calcium supplements, or antacids, as these interfere with absorption 3
• The simvastatin 10mg can be taken at a different time of day (typically evening) to avoid any potential interaction 3

Common Pitfalls to Avoid

• Do not recheck TSH before 6-8 weeks—adjusting doses too frequently before reaching steady state leads to inappropriate dose changes 1, 2
• Do not aim for TSH suppression (TSH <0.1 mIU/L) in this patient, as she does not have thyroid cancer and suppression increases risk of atrial fibrillation and osteoporosis 1
• Do not attribute all symptoms to thyroid until TSH normalizes—fatigue and other symptoms should improve within 6-8 weeks of adequate replacement 1

Expected Outcomes

With proper treatment, the patient should experience:

• Normalization of TSH to 0.5-4.5 mIU/L within 6-8 weeks 1, 2
• Improvement in hypothyroid symptoms (if present) within 6-8 weeks 1
• Potential improvement in liver enzymes as thyroid function normalizes 1
• Stabilization of lipid profile (already normal, but hypothyroidism can worsen lipids) 1

Your clinical judgment was sound—proceed confidently with the 88mcg daily dosing and recheck in 6-8 weeks.