Ultrasonographic Assessment of Uterine and Ovarian Structural Changes during the Menstrual Cycle in Relation to Hormonal Variations.

The menstrual cycle is a complex physiological process regulated by intricate hormonal interactions between the hypothalamus, pituitary gland, and ovaries, leading to cyclical changes in the uterus and ovaries.[ 1 2 ] These structural modifications are essential for preparing the endometrium for potential implantation and ensuring proper follicular development and ovulation.[ 3 ] Assessing these changes is crucial for understanding reproductive health, diagnosing menstrual irregularities, and managing infertility. Ultrasonography has emerged as a noninvasive and reliable method for visualizing dynamic changes in the female reproductive system throughout the menstrual cycle.[ 4 5 ] It provides detailed insights into variations in endometrial thickness, follicular growth, and corpus luteum formation, which are indicative of underlying hormonal fluctuations.[ 6 ] By correlating ultrasonographic findings with serum hormone levels, clinicians can better comprehend normal and abnormal menstrual patterns.[ 7 ] Previous studies have demonstrated significant changes in the uterus and ovaries during different phases of the menstrual cycle.[ 8 ] However, variations in these findings based on population, hormonal assays, and ultrasonographic methods necessitate further exploration. Understanding these structural and hormonal dynamics is particularly relevant for diagnosing conditions like polycystic ovarian syndrome, luteal phase defects, and unexplained infertility.[ 9 ]

The study included 50 women aged 20–35 years (mean age: 26.8 ± 4.3 years) with an average menstrual cycle length of 29.2 ± 1.4 days. All participants completed the study without any dropouts. Table 1 summarizes the ultrasonographic findings across the three phases of the menstrual cycle. Endometrial thickness increased significantly from the follicular phase (4.5 ± 0.8 mm) to the luteal phase (10.2 ± 1.1 mm, P < 0.001). The dominant follicle diameter peaked during the ovulatory phase (18.5 ± 2.0 mm) and was replaced by the corpus luteum in the luteal phase (14.0 ± 1.5 mm, P < 0.05). Ultrasonographic changes in uterine and ovarian parameters during the menstrual cycle Hormonal fluctuations during the menstrual cycle are presented in Table 2 . Estrogen levels were highest in the ovulatory phase (mean: 210 ± 30 pg/mL), while LH levels peaked during the ovulatory phase (mean: 26 ± 4 IU/L, P < 0.001). Progesterone levels were significantly elevated in the luteal phase (mean: 16 ± 2 ng/mL, P < 0.001). Hormonal levels across the menstrual cycle A significant positive correlation was observed between estrogen levels and endometrial thickness during the follicular and ovulatory phases ( r = 0.78, P < 0.01). Similarly, luteal-phase progesterone levels showed a strong association with corpus luteum size ( r = 0.83, P < 0.001). These findings highlight the dynamic structural changes in the uterus and ovaries in response to hormonal variations during the menstrual cycle [ Tables 1 and 2 ].

In conclusion, this study demonstrated significant correlations between hormonal fluctuations and ultrasonographic changes in the uterus and ovaries across the menstrual cycle. These findings reinforce the importance of hormonal balance in maintaining menstrual health and provide a foundation for further investigations into menstrual irregularities and infertility. There are no conflicts of interest.

The progressive increase in endometrial thickness from the follicular to the luteal phase observed in this study aligns with previous research highlighting estrogen-driven proliferation and progesterone-induced secretory transformation of the endometrium.[ 1 2 ] Estrogen levels were significantly higher during the follicular phase, contributing to the initial endometrial thickening, while elevated progesterone levels in the luteal phase promoted endometrial maturation.[ 3 4 ] These changes are essential for implantation and the maintenance of early pregnancy. The dominant follicle diameter peaked during ovulation, as reported in earlier studies.[ 5 6 ] The rapid rise in LH during the ovulatory phase triggered the final maturation and rupture of the dominant follicle, which was subsequently replaced by the corpus luteum in the luteal phase.[ 7 ] The corpus luteum diameter observed in this study was consistent with its role as a transient endocrine structure secreting progesterone to support the luteal phase.[ 8 ] Our findings showed a significant positive correlation between estrogen levels and endometrial thickness during the follicular and ovulatory phases. This agrees with prior research emphasizing estrogen’s proliferative effect on the endometrium.[ 9 10 ] Similarly, the strong association between progesterone levels and corpus luteum size during the luteal phase corroborates previous studies on luteal-phase endocrinology.[ 1 ] The study also highlights the utility of ultrasonography as a noninvasive, reliable tool for assessing menstrual cycle dynamics. Transvaginal ultrasonography provided precise measurements of uterine and ovarian changes, facilitating the diagnosis of conditions like luteal phase defects and anovulation.[ 2 3 ] However, variations in ultrasonographic findings across populations underscore the need for individualized clinical assessments.[ 4 ]

This was a prospective observational study conducted over a period of six months at a tertiary-care hospital. The study included 50 women aged 20–35 years with regular menstrual cycles (28–35 days) and no history of hormonal therapy or reproductive disorders in the preceding six months. Women with polycystic ovary syndrome, endometriosis, uterine anomalies, or systemic illnesses were excluded to ensure the reliability of the findings. Participants underwent ultrasonographic evaluations during three distinct phases of the menstrual cycle: Follicular phase (days 5–7): To assess baseline endometrial thickness and ovarian follicular development. Ovulatory phase (days 12–14): To measure the dominant follicle diameter and monitor ovulation. Luteal phase (days 21–23): To evaluate the corpus luteum and endometrial thickening. Follicular phase (days 5–7): To assess baseline endometrial thickness and ovarian follicular development. Ovulatory phase (days 12–14): To measure the dominant follicle diameter and monitor ovulation. Luteal phase (days 21–23): To evaluate the corpus luteum and endometrial thickening. Both transabdominal and transvaginal ultrasonography were performed using a high-resolution ultrasound system equipped with a 7.5-MHz transducer. Measurements included endometrial thickness, the diameter of the dominant follicle, and corpus luteum dimensions. All scans were conducted by a single experienced radiologist to minimize interobserver variability. Venous blood samples were collected during each phase of the menstrual cycle to measure serum levels of: Estrogen: Using enzyme-linked immunosorbent assay (ELISA). Progesterone: Quantified via chemiluminescence immunoassay. Luteinizing hormone (LH): Measured using an immunoradiometric assay. Estrogen: Using enzyme-linked immunosorbent assay (ELISA). Progesterone: Quantified via chemiluminescence immunoassay. Luteinizing hormone (LH): Measured using an immunoradiometric assay. All samples were processed in a certified laboratory to ensure accuracy and consistency. Data were analyzed using SPSS software (version 25.0).