What are the next steps to address hair loss and adjust my Levothyroxine and Mirena (levonorgestrel) regimen given my recent lab results?

Thyroid Management and Hair Loss Evaluation

Your Current Thyroid Status

Your thyroid function is well-controlled on your current levothyroxine dose. With a TSH of 1.5 mIU/L and free T4 of 15.4 pmol/L (assuming standard units), both values fall within the normal reference range, indicating adequate thyroid hormone replacement 1. No adjustment to your levothyroxine dose is needed at this time 1.

Essential Next Steps for Hair Loss Evaluation

You must check vitamin D, vitamin B12, and ferritin levels immediately, as these nutritional deficiencies are common reversible causes of hair loss that require separate treatment from thyroid management. 2, 3

Why These Tests Matter for Hair Loss

• Ferritin deficiency is one of the most common nutritional causes of telogen effluvium (diffuse hair shedding) and can occur even when thyroid function is optimized 2, 3
• Vitamin D and B12 deficiencies can independently contribute to hair loss and are frequently overlooked in patients focusing solely on thyroid issues 2
• These deficiencies will not improve with levothyroxine adjustment alone and require targeted supplementation 2, 3

Understanding Your Hair Loss in Context

Thyroid-Related Hair Loss

• Hair loss can occur as a temporary side effect when starting levothyroxine, typically resolving within the first few months of therapy 4
• Untreated or undertreated hypothyroidism causes hair loss, but your current thyroid levels indicate this is not the issue 5
• Once thyroid hormone levels normalize (as yours have), thyroid-related hair loss should improve within 2-4 months 5

Mirena and Hair Loss Considerations

• Hormonal contraceptives, including levonorgestrel-containing IUDs like Mirena, can trigger telogen effluvium in susceptible individuals 2, 3
• Hair loss from hormonal changes typically becomes evident 2-4 months after starting treatment, which may align with your Mirena insertion timeline 3
• This represents a drug-induced telogen effluvium where hair follicles are prematurely pushed into the resting phase 3

Monitoring Protocol Going Forward

Current Thyroid Monitoring Schedule

• Continue monitoring TSH every 6-12 months while on a stable levothyroxine dose, or sooner if symptoms change 1
• No need for more frequent thyroid testing unless you develop symptoms of hypo- or hyperthyroidism 1

Critical Pitfall to Avoid

• Do not increase your levothyroxine dose in an attempt to treat hair loss when your TSH is already in the normal range 1
• Overtreatment with levothyroxine (causing TSH suppression) increases risks for atrial fibrillation, osteoporosis, and fractures, particularly in the long term 1
• Approximately 25% of patients on levothyroxine are inadvertently overtreated, leading to serious complications 1

Specific Action Plan

1. Order laboratory tests immediately: vitamin D (25-OH), vitamin B12, and ferritin 2, 3
2. Continue current levothyroxine dose without adjustment 1
3. Document timeline: Note exactly when hair loss began relative to starting/switching levothyroxine and Mirena insertion 3
4. Assess pattern: Determine if hair loss is diffuse (all over scalp) versus patterned, as this helps distinguish telogen effluvium from other causes 2, 3
5. Consider Mirena as potential contributor if hair loss began 2-4 months after insertion 3

When to Reassess Thyroid Dosing

• Only if TSH rises above 4.5-10 mIU/L on repeat testing would dose adjustment be considered 1
• Only if TSH falls below 0.5 mIU/L would dose reduction be necessary to prevent overtreatment complications 1
• Your current TSH of 1.5 mIU/L represents optimal replacement therapy 1