European Journal of Cardiovascular Medicine

The thyroid gland is integral to metabolic and reproductive regulation through the secretion of thyroid hormones, triiodothyronine (T3) and thyroxine (T4), controlled by thyroid-stimulating hormone (TSH) from the pituitary gland [Krassas et al., 2000; 1]. Hypothyroidism, characterized by inadequate thyroid hormone production, stems from causes such as autoimmune thyroiditis (Hashimoto’s disease), iodine deficiency, or iatrogenic factors like thyroidectomy, and disproportionately affects women due to higher autoimmune susceptibility [Sharma et al., 2021; 2]. Globally, hypothyroidism prevalence ranges from 2–5%, with women comprising the majority of cases [Sharma et al., 2021; 2]. In reproductive-age women, it disrupts the hypothalamic-pituitary-ovarian axis, altering gonadotropin-releasing hormone (GnRH) pulsatility, estrogen metabolism, and progesterone levels, which manifest as menstrual irregularities [Pop et al., 2023; 3].

Menstrual irregularities, including oligomenorrhea (cycles >35 days), menorrhagia (excessive or prolonged bleeding), polymenorrhea (cycles <21 days), and amen5.7orrhea (absence of periods), affect up to 30% of women in their reproductive years, contributing to infertility, chronic anemia, and diminished quality of life [Thomas et al., 2025; 4]. Hypothyroidism is a well-documented cause, with studies reporting menstrual irregularities in 23.4% of hypothyroid women compared to 12% in euthyroid controls [Joshi et al., 1997; 5]. In younger populations, severe hypothyroidism may present with menorrhagia as a primary symptom [Quintino-Moro et al., 2022; 6]. In India, persistent iodine deficiency in certain regions, despite national iodization efforts, exacerbates thyroid disorders, contributing significantly to gynecological complaints [Gupta et al., 2019; 7]. A study in rural India found hypothyroidism in 60.4% of women with irregular heavy bleeding compared to 49.2% with normal cycles [Padmavathi et al., 2020; 8].

Subclinical hypothyroidism, defined by elevated TSH with normal free T4 levels, is particularly prevalent, affecting up to 14% of reproductive-age women and often remaining undiagnosed until reproductive issues emerge [Sharma et al., 2024; 9; Baloch et al., 2011; 10]. The lack of routine thyroid screening in outpatient settings leads to delayed diagnosis and management, compounding complications [Verma et al., 2023; 11]. This study was conducted to determine the prevalence of hypothyroidism in women presenting with menstrual irregularities at the Department of Medicine, Kanti Devi Medical College Hospital and Research Center, a tertiary facility in Mathura, India, serving a semi-urban and rural population. By characterizing the prevalence and patterns of hypothyroidism, the study aims to advocate for integrated thyroid screening to enhance clinical outcomes [Singh et al., 2022; 12].

Study Design and Setting

This prospective cross-sectional study was conducted at the Department of Medicine, Kanti Devi Medical College Hospital and Research Center, Mathura, Uttar Pradesh, India, from June 2024 to April 2025. The institution is a tertiary care center providing affordable healthcare to urban, semi-urban, and rural populations.

Participants

Eligible participants were women aged 18–45 years presenting to the outpatient department with menstrual irregularities persisting for at least three months. Irregularities were defined as oligomenorrhea (cycles >35 days), menorrhagia (bleeding >80 mL or lasting >7 days), polymenorrhea (cycles <21 days), or amenorrhea (no periods for ≥3 months). Exclusion criteria included pregnancy (confirmed by urine hCG test), known thyroid disorders, polycystic ovary syndrome (diagnosed via Rotterdam criteria and ultrasound), hyperprolactinemia, use of hormonal contraceptives or medications affecting thyroid function (e.g., amiodarone, lithium), and comorbidities such as diabetes mellitus, chronic kidney disease, or malignancy [Thomas et al., 2025; 4]. A sample size of 150 was calculated using the formula n = Z²P(1-P)/d², assuming a 25% prevalence from prior studies [Sharma et al., 2021; 2], a 95% confidence level (Z=1.96), and a 5% margin of error (d=0.05). Consecutive sampling was employed until the target was reached.

Data Collection and Investigations

A structured proforma captured demographic details (age, residence, socioeconomic status via Kuppuswamy scale), detailed menstrual history (onset, duration, frequency, volume), and associated symptoms (e.g., fatigue, weight gain, cold intolerance). Anthropometric measurements, including body mass index (BMI), were recorded. Fasting venous blood samples (5 mL) were collected in the morning for thyroid function tests using chemiluminescence immunoassay on a Roche Cobas e411 analyzer. Reference ranges were: TSH 0.4–4.5 mIU/L, free T4 0.8–1.8 ng/dL, and free T3 2.3–4.2 pg/mL. Hypothyroidism was classified per American Thyroid Association guidelines: overt (TSH >4.5 mIU/L, free T4 <0.8 ng/dL) and subclinical (TSH >4.5 mIU/L, normal free T4) [GoodRx, 2024; 14]. All assays were performed in the hospital’s NABL-accredited laboratory with internal quality controls.

Statistical Analysis

Data were entered into Microsoft Excel and analyzed using SPSS version 25.0. Continuous variables were expressed as mean ± standard deviation (SD) or median (interquartile range) if non-normally distributed (assessed by Shapiro-Wilk test). Categorical variables were reported as frequencies and percentages. Comparisons used independent t-tests or Mann-Whitney U tests for continuous data, and chi-square or Fisher’s exact tests for categorical data. Logistic regression adjusted for confounders (age, BMI) to explore associations. A p-value <0.05 was considered significant [Thomas et al., 2025; 4].

A total of 150 women were enrolled, with a mean age of 28.3 ± 6.1 years and a mean BMI of 24.5 ± 4.2 kg/m². Sixty-two percent resided in rural areas, and socioeconomic distribution (Kuppuswamy scale) was 10% upper, 60% middle, and 30% lower class. Menstrual irregularities comprised oligomenorrhea (38%), menorrhagia (42%), and amenorrhea (20%). Thyroid dysfunction was identified in 42 (28%) participants, with hypothyroidism in 36 (24%): 22 (14.7%) subclinical and 14 (9.3%) overt. Hyperthyroidism was observed in 6 (4%) but excluded from primary analysis.

Table 1: Demographic Profile of Study Participants

Table 1 presents the demographic characteristics of 150 women aged 18–45 years presenting with menstrual irregularities assessed using the Kuppuswamy scale. BMI categories follow WHO guidelines. Data are expressed as frequencies and percentages.

Table 2: Distribution of Menstrual Irregularities and Thyroid Status

Table 2 shows the distribution of menstrual irregularities (oligomenorrhea, menorrhagia, amenorrhea) across thyroid status groups among 150 participants. Values are presented as frequencies and percentages.

Table 3: Prevalence of Thyroid Dysfunction

Table 3 summarizes the prevalence of thyroid dysfunction among 150 women with menstrual irregularities, based on thyroid function tests (TSH, free T4, free T3) . Hypothyroidism is classified as subclinical (TSH >4.5 mIU/L, normal free T4) or overt (TSH >4.5 mIU/L, free T4 <0.8 ng/dL).

Table 4: Comparison of Clinical and Biochemical Parameters

Table 4 compares clinical and biochemical parameters between hypothyroid and euthyroid groups among 150 women with menstrual irregularities. Continuous variables are expressed as mean ± SD; categorical variables as frequencies and percentages. P-values were calculated using t-tests for continuous variables and chi-square tests for categorical variables.

Menorrhagia was significantly associated with hypothyroidism (p=0.05). No significant differences were observed in age, residence, or BMI between groups. Logistic regression, adjusted for age and BMI, identified elevated TSH as an independent predictor of menstrual irregularities (OR=2.3, 95% CI: 1.4–3.8, p=0.002).

Figure 1: This chart displays the number of participants in each thyroid status category, with clear labeling and color differentiation. The y-axis represents the number of participants, and the x-axis lists the thyroid status categories.

Figure 2: This grouped bar chart illustrates the number of participants with each type of menstrual irregularity (Oligomenorrhea, Menorrhagia, Amenorrhea) across the three thyroid status groups (Hypothyroid, Euthyroid, Hyperthyroid). The y-axis shows the number of participants, and the x-axis lists the menstrual irregularity types.

The 24% prevalence of hypothyroidism in this cohort is consistent with prior studies reporting 20–40% prevalence among women with menstrual irregularities [Joshi et al., 1997; 5; Sharma et al., 2021; 2]. In India, a study reported a 22.85% prevalence in reproductive-age women, attributed to iodine deficiency and autoimmune thyroiditis prevalent in South Asia [Sharma et al., 2021; 2]. Subclinical hypothyroidism (14.7%) predominated over overt hypothyroidism (9.3%), aligning with its often-asymptomatic nature and frequent underdiagnosis [Sharma et al., 2024; 9; Baloch et al., 2011; 10]. The significant association of menorrhagia with hypothyroidism (p=0.05) may be explained by thyroid hormone effects on coagulation factors (e.g., reduced factor VIII) and endometrial proliferation, leading to heavy menstrual bleeding [Padmavathi et al., 2020; 8].

Compared to global data, where hypothyroidism prevalence in women with menstrual irregularities ranges from 23–30% [Krassas et al., 2000; 1; Quintino-Moro et al., 2022; 6], the findings suggest a comparable burden in India, potentially exacerbated by regional factors like iodine deficiency [Gupta et al., 2019; 7]. The higher prevalence of subclinical hypothyroidism underscores the need for sensitive screening, as it may progress to overt disease and contribute to reproductive complications, including infertility [Sharma et al., 2024; 9]. The lack of association with age or BMI in this study contrasts with some reports suggesting higher hypothyroidism rates in older or obese women, possibly due to the relatively young cohort and controlled exclusion criteria [Verma et al., 2023; 11].

Limitations include the single-center design, which may limit generalizability to other populations, and the exclusion of comorbidities like PCOS, which could coexist with hypothyroidism. Additionally, the study did not assess anti-thyroid antibodies, which could clarify autoimmune contributions. Future research should incorporate longitudinal follow-up to evaluate treatment outcomes and include multicenter data to enhance generalizability. These findings strongly support routine thyroid function testing in women with menstrual irregularities to facilitate early diagnosis and reduce complications such as infertility and anemia [Singh et al., 2022; 12; Verma et al., 2023; 11].

The 24% prevalence of hypothyroidism, with a predominance of subclinical cases, highlights its significant role in menstrual irregularities. Routine thyroid function testing is recommended for women presenting with menstrual complaints to enable early intervention and prevent long-term reproductive and systemic complications.

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