Dhillon-Smith RK, Tobias A, Smith PP, et al. - Via performing an observational cohort study of women aged 16 to 41 years with history of miscarriage or subfertility trying for a pregnancy, researchers investigated the prevalence of and factors linked with different thyroid dysfunction phenotypes in women who are asymptomatic preconception. They assessed data concerning thyroid function and thyroid peroxidase antibody (TPOAb) of 19,213 and 19,237 women, respectively. Findings revealed a low prevalence of undiagnosed overt thyroid disease. Common occurrence of  subclinical hypothyroidism (SCH) and TPOAb was observed, particularly among women with higher BMI or of Asian ethnicity. To describe SCH outcomes in a significant proportion of women potentially necessitating levothyroxine treatment, a TSH cutoff of 2.50 mIU/L is suggested.