PREVALENCE OF SUBCLINICAL HYPOTHYROIDISM IN REPRODUCTIVE-AGED WOMEN AND ITS ASSOCIATION WITH MENSTRUAL IRREGULARITIES

Background: Subclinical hypothyroidism (SCH), characterized by elevated TSH with normal thyroid hormone levels, often remains undiagnosed despite its potential effects on reproductive health. In women of reproductive age, even mild thyroid dysfunction can disrupt the hypothalamic-pituitary-ovarian axis, contributing to menstrual irregularities that impact fertility and overall quality of life. Objective: To determine the prevalence of subclinical hypothyroidism and evaluate its association with menstrual irregularities among women aged 18–40 years. Methods: A cross-sectional study was conducted over eight months in tertiary care hospitals in Lahore, Pakistan, enrolling 422 women aged 18–40 years. Participants were assessed using a structured questionnaire and underwent serum TSH, FT4, and FT3 testing. Subclinical hypothyroidism was defined as TSH >4.0 mIU/L with normal FT4 and FT3. Menstrual patterns were categorized as regular or irregular. Data were analyzed using SPSS v26 with Chi-square and logistic regression tests; significance was set at p<0.05. Results: The prevalence of subclinical hypothyroidism was 19.9% (n=84). Among these, 57.1% reported menstrual irregularities, compared to 17.8% in the euthyroid group. Women with SCH had 6.2 times higher odds of experiencing menstrual disturbances (95% CI: 3.7–10.5, p<0.001), independent of age and BMI. Conclusion: Subclinical hypothyroidism is significantly associated with menstrual irregularities in reproductive-aged women. Routine thyroid screening should be considered in women presenting with menstrual disturbances to enable early diagnosis and appropriate management.