Levothyroxine Replacement Therapy and Overuse: A Timely Diagnostic Approach.

Area of Science:

• Endocrinology
• Pharmacology

Background:

• Levothyroxine (LT4) is a widely prescribed medication, with long-term use common in approximately 90% of patients.
• Evidence suggests potential overuse of LT4, particularly when the initial indication for treatment is not well-established or documented.

Purpose of the Study:

• To evaluate the necessity of long-term levothyroxine (LT4) supplementation.
• To identify potential prognostic factors associated with continued LT4 therapy.

Main Methods:

• A prospective cohort study involving 291 patients on LT4 therapy without a confirmed diagnosis of hypothyroidism.
• Treatment was paused for 6-8 weeks, with thyrotropin (TSH) and free thyroxine levels measured before and after discontinuation.
• Thyroid ultrasound was performed, and hypothyroidism was defined as a TSH value of ≥4.5 IU/mL.

Main Results:

• Of 291 participants, 114 (39.2%) became hypothyroid (Group A) and 177 (60.8%) remained euthyroid off LT4 (Group B).
• Group A showed a significantly higher prevalence of diffuse inhomogeneous echogenicity on ultrasound compared to Group B.
• No significant differences were observed between groups regarding sex, family history, age, BMI, treatment duration, or thyroid autoantibodies.

Conclusions:

• Findings indicate significant overuse of levothyroxine (LT4) therapy.
• Emphasizes the importance of establishing a firm diagnosis before initiating LT4 and conducting periodic reassessments for treatment necessity.
• Recommends a 6-8 week LT4 discontinuation trial with TSH monitoring as a first-line approach to decrease overuse.