Effects of acarbose and metformin on thyroid function and thyroid hormone sensitivity in type 2 diabetes patients: a post-hoc analysis of the MARCH study.

Purpose: While metformin is known to regulate thyroid stimulating hormone (TSH) levels, the effects of acarbose on thyroid function remain unreported. Our study was designed to evaluate the impact of acarbose and metformin on thyroid function and thyroid hormone sensitivity in type 2 diabetic patients.
Methods: In the MARCH study, 788 patients with type 2 diabetes were randomly assigned to treat with acarbose (300 mg) or metformin (1,500 mg) for 48 weeks. Thyroid function was assessed at baseline, 24 weeks, and 48 weeks, and the thyroid feedback quantile index (TFQI) and parameterized thyroid feedback quantile index (PTFQI) were calculated. Generalized estimating equations adjusted for confounders were used to analyze changes over time.
Results: Eighty-four patients with subclinical hypothyroidism (SCH) exhibited a decrease in TSH levels (p = 0.001) with no significant differences between the two treatment groups (p = 0.460). Both TFQI (p = 0.029) and PTFQI (p < 0.001) also decreased over time. Mediation analysis revealed that these change over time were not mediated by BMI (all p < 0.05). Among the 489 euthyroid subjects, no significant changes in TSH levels were observed (p > 0.05). Stratification by baseline TSH levels revealed significant increases in TSH, TFQI, and PTFQI (all p < 0.05) in the normal-low TSH group and significant decreases in PTFQI (all p < 0.05) in the normal-high TSH group after treatment with acarbose and metformin.
Conclusions: Acarbose and metformin have similar buffering effects on TSH levels, the TFQI and the PTFQI. In patients with lower TSH levels, acarbose and metformin do not further decrease TSH levels.
Clinical Trial Registry Number: ChiCTR-TRC-08000231.
Competing Interests: Declarations. Ethical approval: Informed consent was obtained from every patient, and ethical approval was granted by the ethics committees at each clinical site in multiple centres. The study was conducted in accordance with the principles of the Declaration of Helsinki and Good Clinical Practice Guidelines. Prior presentation: None. Competing interests: The authors declare no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
(© 2024. The Author(s), under exclusive licence to Italian Society of Endocrinology (SIE).)