Effect of the Cut-Off Level for Thyroid-Stimulating Hormone on the Prevalence of Subclinical Hypothyroidism among Infertile Mexican Women

Abstract

The primary aim of this study was to compare the prevalence of subclinical hypothyroidism (SCH) using two different cut-off levels for TSH values (≥2.5 mIU/L versus ≥4.1 mIU/L). The secondary objective was to analyze the clinical-biochemical characteristics in women with and without SCH. This was a retrospective cross-sectional study. In total, 1496 Mexican women with infertility were included: Group 1, women with TSH levels ranging between 0.3 and 2.49 mIU/L, n = 886; Group 2, women with TSH between 2.5 and 4.09 mIU/L, n = 390; and Group 3, women with TSH ≥4.1 mIU/L n = 220. SCH prevalence was 40.7% (CI 95%: 38.3–43.3%) with TSH cut-off ≥ 2.5 mIU/L, and 14.7% (CI 95%: 12.7–16.5%) with TSH cut-off ≥ 4.1 mIU/L, (p = 0.0001). The prevalence of overweight was higher in Group 2 than in Groups 1 and 3. Thyroid autoimmunity, obesity and insulin resistance were higher in Group 3 than in Group 1 (p < 0.05). No other differences were observed between groups. Conclusions: The prevalence of SCH in our selected patients increased almost three times using a TSH cut-off ≥ 2.5 mIU/L compared with a TSH cut-off ≥ 4.1 mIU/L. Women with TSH ≥4.1 mIU/L compared with TSH cut-off ≤ 2.5 mIU/L more often presented with obesity, thyroid autoimmunity and insulin resistance.

Thyroid Dysfunction, Total Cholesterol Levels and Anthropometric Status in Women of Reproductive Age in Iodine Deficient Area of Prambanan Sub-District, Sleman Regency, Indonesia

“…Thyroid dysfunction was defined as: (1) subclinical hypothyroidism, if TSH level above reference interval, with FT4 was still in the normal reference range; (2) clinical hypothyroidism was indicated by the increase of TSH and the decrease of FT4; (3) subclinical hyperthyroidism if TSH level below reference value, with FT4 was still in the normal reference interval; (4) clinical hyperthyroidism was indicated by the decrease of TSH and the increase of FT4. Meanwhile the normal thyroid function if both TSH and FT4 were still in the normal reference interval (Arce-Sánchez et al 2021). In this study, thyroid dysfunction was classified as "Yes" (for subjects with subclinical hypothyroidism, clinical hypothyroidism, subclinical hyperthyroidism, and clinical hyperthyroidism) and "No" (for subject with normal thyroid function).…”

Exploring associations of anthropometric parameters and serum triglycerides with serum thyroid hormones in young women

“…Given that the initial criteria qualified the young women to the healthy group, the question arises which of the presented cut-off values may be more effective for diagnosing latent thyroid diseases and their biological effects in this age group. According to the opinion of some authors, the TSH cut-off value of > 4.0 mU/L is sufficient for the selection of impaired thyroid function and is commonly used in clinical routine 34 . On the other hand, an increase in TSH > 2.5 mU/L allows for a more sensitive distinction of young women during the pregnancy planning period, with an indication of an increase in the risk of health disorders in later life and during pregnancy 5 , 8 , 9 .…”