[Once weekly L-thyroxine treatment in non-compliance: A case report]

Area of Science:

• Endocrinology
• Pharmacology

Background:

• Non-adherence to L-thyroxine (LT4) is a primary driver of discordance between elevated thyrotropin (TSH) and prescribed LT4 dosage in hypothyroidism management.
• Identifying non-adherence is crucial for effective thyroid hormone replacement therapy.

Observation:

• A 36-year-old patient with post-thyroidectomy hypothyroidism presented with persistently high TSH (100-400 mUI/L) despite a high daily LT4 dose (300 μg) and triiodothyronine (T3) supplementation (75 μg).
• An oral LT4 loading test yielded normal results, and TSH normalized with a weekly oral LT4 dose of 1000 μg, suggesting non-adherence to the daily regimen.
• This case highlights the utility of oral LT4 testing in diagnosing non-adherence.

Findings:

• The L-thyroxine oral loading test serves as a reliable diagnostic tool for non-adherence in patients with suspected hypothyroidism treatment failure.
• Weekly high-dose oral or parenteral LT4 administration can effectively normalize TSH levels in non-adherent patients.
• Conventional causes like drug interactions and malabsorption must be excluded before diagnosing non-adherence.

Implications:

• This diagnostic strategy allows for tailored hypothyroidism treatment, moving beyond standard daily dosing when necessary.
• Individualized treatment plans, including weekly LT4 administration, can improve therapeutic outcomes and patient adherence.
• The findings support a case-by-case approach to L-thyroxine therapy, optimizing management for non-adherent patients.