Measuring Testosterone in Women
Introduction to Testosterone
Testosterone is a hormone found in both men and women. It is important for many body functions. Measuring testosterone levels in women can be hard because their levels are lower than men's and can change throughout their menstrual cycle.
How Menstrual Cycle Affects Testosterone
Testosterone levels in women change during the menstrual cycle. The highest levels are usually around ovulation. Studies show that both total testosterone (TT) and free testosterone (FT) peak during the middle of the cycle. However, testosterone levels vary during the rest of the cycle. Some studies find higher levels in the follicular phase, while others find higher levels in the luteal phase. Many studies show no significant change throughout the cycle. These differences can be due to study methods, participant differences, and testing techniques. Despite these variations, the mid-cycle peak is a common finding.
Normal Testosterone Ranges in Women
Normal testosterone levels in women depend on their age and menstrual cycle phase. Using advanced methods like liquid chromatography-tandem mass spectrometry (LC-MS/MS), researchers have found the following ranges for healthy women aged 18–49:
- Total testosterone: 15-46 ng/dL
- Free testosterone: 1.2-6.4 pg/mL
- Bioavailable testosterone: 1.12–7.62 ng/dL
During the menstrual cycle, total testosterone rises from about 15.6 ng/dL in the early luteal phase to a peak of 43.6 ng/dL at mid-cycle. Free testosterone rises from 9.00 pg/mL to 15.6 pg/mL. Testosterone levels also decline with age, with lower levels after menopause compared to reproductive years. Establishing exact reference ranges is challenging due to assay differences, menstrual cycle changes, and factors like body mass index.
Testosterone Peaks During Ovulation
Testosterone levels in women show a small peak around ovulation, usually at the middle of the cycle. The increase in luteinizing hormone (LH) before ovulation is what causes this peak. The increase varies between individuals, but studies using sensitive methods like LC-MS/MS consistently detect this mid-cycle peak. The day-to-day variability in testosterone levels is often greater than the ovulatory peak itself, making it hard to see in some cases.
Measuring Testosterone: Mass Spectrometry vs. Immunoassays
Two common methods for measuring testosterone are mass spectrometry and immunoassays. Immunoassays, like ELISA, are high-throughput, low-cost, and easy to use but can lack specificity. Mass spectrometry, such as LC-MS/MS, provides higher sensitivity and specificity and can measure multiple analytes simultaneously. However, it has higher costs and requires more expertise.
Importance of Mass Spectrometry Sensitivity
Mass spectrometry is crucial for accurately measuring low testosterone levels in women. Traditional immunoassays often lack the precision needed. Mass spectrometry methods like LC-MS/MS offer superior sensitivity, enabling better assessment of androgen status in women and diagnosing testosterone imbalances. This helps establish appropriate reference ranges and guide clinical decisions.
Luteal Phase Hormonal Shifts
After ovulation, the luteal phase begins and lasts until the next menstrual period. Progesterone levels rise significantly due to the corpus luteum. Estrogen levels also increase during the mid-luteal phase before declining. If pregnancy does not occur, both progesterone and estrogen levels drop sharply, leading to menstruation. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels decrease during the luteal phase.
Follicular Phase Testosterone Trends
During the follicular phase, starting from the first day of menstruation to ovulation, testosterone levels tend to be lower compared to other phases. However, they gradually increase as the phase progresses, peaking before ovulation. Women with longer follicular phases often have higher testosterone levels, while shorter phases are associated with lower levels.
Testosterone Decline After Menopause
Testosterone levels decline with age, reaching lower levels after menopause. This decrease can lead to symptoms like reduced bone density, lower energy, and depression. Some doctors prescribe testosterone therapy to alleviate menopausal symptoms, although there is no FDA-approved testosterone product for women.
Sleep Patterns and Hormone Levels
Sleep and hormone levels are closely linked. Circadian rhythms have an impact on melatonin, which regulates sleep. Hormonal changes during the menstrual cycle can affect sleep. Progesterone, which peaks during the luteal phase, can cause drowsiness, while its drop before menstruation can lead to sleep disturbances. Poor sleep can disrupt hormone production, leading to health issues like metabolic problems and increased appetite.
Optimal Hormone Testing Timing in Women
The best time to measure hormones depends on the specific hormone and the purpose of testing. For fertility assessment, FSH and estradiol are tested on day 3 of the cycle. Estradiol and progesterone are measured around days 19–22 to check for luteal phase defects. LH levels peak around ovulation, while progesterone rises after ovulation. Perimenopausal hormone patterns are erratic, making single-day measurements less reliable.
Menstrual Cycle Hormone Imbalance Symptoms
Hormonal imbalances can cause irregular periods, heavy bleeding, and missed periods. Skin issues like acne, digestive problems, mood swings, and sleep disturbances are common. Other symptoms include low libido, vaginal dryness, infertility, weight changes, and hair growth or loss. Persistent or severe symptoms may indicate an underlying endocrine disorder that needs further evaluation.
