CAN BLOOD SAMPLES BE COLLECTED ON ANY DAY OF THE MENSTRUAL CYCLE FOR HORMONAL TESTS?

CAN BLOOD SAMPLES BE COLLECTED ON ANY DAY OF THE MENSTRUAL CYCLE FOR HORMONAL TESTS?
I want to explain a controversy about the best time to collect blood for hormonal assays.
Most of the time, when patients are told to go and run these tests at another center, they may be sent back with the information that the tests cannot be done at any time during the cycle, except on day 2 or 3 of the menstrual cycle, while progesterone should be tested on day 21.
I want to tell you that, with the advancement of technology, blood samples for fertility investigations can be collected at different times during a woman’s menstrual cycle and not necessarily only on the days traditionally recommended. However, the appropriate timing still depends on the particular hormone being tested and the reason for the investigation.
The reason blood samples were traditionally collected on day 2 or 3 was mainly to assess ovarian function and ovarian reserve—to have an idea of the number of eggs remaining in the woman’s ovaries. FSH and LH were commonly assessed during this period because of their relationship with ovarian function during the early part of the menstrual cycle.
Fertility investigations have also advanced with the introduction of Anti-Müllerian Hormone (AMH), which is generally more stable throughout the menstrual cycle and is commonly used as part of the assessment of ovarian reserve.
If a patient is being re-evaluated, however, there may be a specific reason why the sample should be collected on day 2 or 3. For example, a patient who is being treated for PCOS/PMOS may be asked to have the test performed on those specific days so that the results can be properly monitored and compared during treatment.
Therefore, the timing of hormonal testing should be determined based on the particular test being carried out, the reason for the investigation, and the advice of the healthcare professional managing the patient.