Ultrasound Characterization of Ovarian Follicle Dynamics in Women With Amenorrhea

Overview

In women with regular menstrual cycles, antral follicles have been shown to grow in synchronous cohorts, called waves, 2-3 times in a menstrual cycle. It is unknown whether these waves of follicle growth also occur in women with amenorrhea or if there is abnormal/absent follicle growth. Further, oligo- or amenorrhea has been associated with metabolic disturbances, such as over- or under-nutrition, central obesity and insulin resistance. Yet, mechanisms whereby metabolic factors influence folliculogenesis in women are poorly understood. To understand potential mechanisms, the investigators plan to characterize follicle growth dynamics in women with or without regular menstrual cycles and identifying key metabolic differences in these women which may be important in normal follicle development and fertility.

In the ovaries, eggs rest in fluid filled sacs called follicles. When follicles grow they form small fluid-filled cysts that can be easily seen when we use ultrasound to view the ovaries. In women with regular menstrual cycles, groups of 10 to 20 follicles grow and regress at 2 or 3 different times during their cycle (usually over a 28- day period). Several of these follicles grow to a stage where they begin to develop the potential to ovulate - but in general only one follicle is chosen to ovulate. Thus, at any given time during the menstrual cycle, numerous fluid-filled follicles can be visualized in a woman's ovaries at various stages of development using transvaginal ultrasonography. In women with absent or infrequent menstrual cycles, very little is known about the growth patterns of their follicles and how factors such as metabolic hormones, might play a role in the failure to ovulate. Being underweight or overweight increases your chances of having irregular or absent menstrual cycles and that a history of abnormal reproductive function compounds a woman's risk for chronic diseases such as infertility, diabetes, hypertension, atherosclerosis and certain cancers. This is particularly the case for women with polycystic ovary syndrome (PCOS) that have menstrual cycles that appear to worsen or improve depending on their body weight and metabolic status. PCOS is an endocrine disorder that affects 6-12% of reproductive-aged women within the general population. The hallmark features of PCOS are menstrual irregularity, increased levels of androgens, and polycystic ovaries. The current diagnostic criteria require 2 out of 3 of these features to be present for the diagnosis, therefore a number of phenotypes of PCOS exist. However, the metabolic and reproductive differences across the phenotypic spectrum of PCOS are not well understood. Women with PCOS characteristically have polycystic ovaries, where up to 10 times more follicles are present in the ovary at any given time. Further, the follicle-size populations and overall distribution throughout the ovary varies in women - follicles may be situated around the periphery of the ovary or may be distributed throughout the ovary. Presumably these small follicles are arrested in development - but emerging data from the Lujan laboratory suggest that this is not the case. It is assumed that ovulation does not occur and that follicles do not grow in a normal wave pattern. In truth, no study has ever looked to see whether follicles are actually growing, regressing or are arrested in women with irregular/absent menstrual cycles. By comparing follicle wave dynamics, reproductive hormones and markers of metabolism in women with regular and irregular menstrual cycles, the researchers plan to identify what factors might explain why fertility potential and long-term health are compromised in some women but not in others. Further, we will determine if any of these metabolic factors are unique to PCOS representing specific metabolic risks or follicle growth impairment. The ultimate goal of this research is to understand how body composition, nutrition and metabolism regulate follicle development in women so we can better develop lifestyle and drug therapies to help women preserve their fertility and long-term health. Since obesity has recently become the leading cause of infertility in North America, these studies are especially important. To accomplish our objective, the investigators plan to recruit up to 40 women with regular menstrual cycles and up to 40 women with irregular/absent menstrual cycles. Our goal is to recruit an equal number of women in each group such that they are matched for age (18 - 35 years old) and body mass index (BMI; Normal weight = 18 - 24 kg/m2; Overweight = 25 - 29 kg/m2; Obese = 30kg/m2). Women will undergo serial ultrasonographic of their ovaries every other day from ovulation to ovulation in women with regular menstrual cycles or for 5 weeks in women with cycle irregularity. Blood samples will be collected at each visit. Ultrasound scans of the ovaries will be assessed for the total number, size, and distribution of follicles using ultrasound imaging techniques. Blood samples collected will be assayed to determine serum concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol, progesterone, anti-müllerian hormone (AMH), and inhibin B. During day 3-5 in women with regular menstrual cycles or at a time where no dominant follicle or corpus luteum is present, an early morning visit will be conducted to assess the following metabolic parameters : (1) 75-gram oral glucose tolerance test to characterize glucose and insulin dynamics at 0, 30, 60, 90, and 120 minutes post-glucose ingestion; (2) dual X-ray absorptiometry (DXA) scan to quantify body fat and lean muscle distribution; (3) vitals and anthropometry assessment to measure waist and hip circumference, height, weight, blood pressure, and heart rate, and (4) fasting blood tests to detect serum concentrations of androgens (i.e., total testosterone, androstenedione, free androgen index) and serum markers of metabolic syndrome (i.e., lipids and hemoglobin A1C); (5) optional subcutaneous fat biopsy to analyze fat cells, which represent a site of reproductive hormone synthesis.