From the Guidelines
The appropriate time to check Follicle-Stimulating Hormone (FSH), Luteinizing Hormone (LH), and estrogen levels in the evaluation of irregular menstrual cycles is during the early follicular phase, specifically between days 2-4 of the menstrual cycle, as this provides the most accurate baseline hormonal assessment 1. When evaluating patients with irregular menstrual cycles, it is essential to consider the timing of hormonal assessments to ensure accurate diagnosis and treatment.
- The early follicular phase, between days 2-4 of the menstrual cycle, is the ideal time for checking FSH, LH, and estrogen levels, as hormone levels are relatively stable during this period.
- If the patient is amenorrheic, these tests can be performed at any time, but it is crucial to consider the clinical context and presence of other symptoms or signs of hormonal imbalance.
- The LH to FSH ratio, which is often elevated in PCOS patients, can be a useful diagnostic tool, with a ratio exceeding 2 being suggestive of PCOS, while a ratio less than 1 is more commonly seen in functional hypothalamic amenorrhea (FHA) patients 1.
- It is also important to note that hormone levels fluctuate significantly throughout the menstrual cycle, with FSH and LH surging at mid-cycle during ovulation, and estrogen levels gradually rising during the follicular phase and peaking just before ovulation.
- Therefore, testing at other times may lead to misinterpretation of results and potentially incorrect diagnosis or treatment decisions, highlighting the importance of standardized timing for hormonal assessments.
From the Research
Hormone Level Variations
- FSH, LH, and estrogen levels can vary throughout the menstrual cycle, making it essential to determine the appropriate time for checking these levels 2, 3.
- The follicular phase is characterized by rising estrogen secretion, while other hormone levels are low 3.
- At ovulation, luteinizing hormone and follicle-stimulating hormone surges are associated with falling estrogen levels 3.
Appropriate Time for Checking Hormone Levels
- Baseline FSH levels are typically measured on days 2-3 of the menstrual cycle 4.
- Response levels of FSH, LH, and 17-beta oestradiol can be measured after administration of clomiphene on days 5-9 of the menstrual cycle 4.
- Daily blood sampling and ultrasound monitoring in the follicular phase can provide a complete endocrine cycle profile 5.
- Hormone levels can be measured at different phases of the cycle, including early follicular, late follicular, LH peak, early luteal, mid-luteal, and late luteal phases 2.
Factors Affecting Hormone Levels
- Age and ovarian reserve can impact FSH levels, with elevated FSH levels indicating a low ovarian reserve 5, 4.
- The clomiphene citrate challenge test can be used to assess future fertility potential and detect diminished ovarian reserve (DOR) 4.
- Irregular menstrual cycles, polycystic ovarian syndrome (PCOS), and high levels of exercise can affect hormone levels and menstrual cycle regularity 6.