Letrozole is a widely used oral medication in fertility treatments to encourage the release of an egg from the ovary, a process known as ovulation induction. While originally approved for treating certain types of breast cancer, its use in fertility care is considered off-label due to its effect on reproductive hormones. The success of this treatment relies heavily on precise timing within the menstrual cycle. Understanding the correct schedule for taking Letrozole is fundamental to maximizing the chance of conceiving.
How Letrozole Stimulates Ovulation
Letrozole is classified as an aromatase inhibitor, meaning it temporarily blocks the enzyme that converts androgens into estrogen. This immediate suppression causes a rapid, temporary drop in circulating estrogen levels. The pituitary gland perceives this low estrogen environment as a sign that ovarian activity is insufficient and increases its production of Follicle Stimulating Hormone (FSH). This surge of FSH promotes the growth and maturation of ovarian follicles. The temporary increase in intraovarian androgens may also enhance the follicles’ sensitivity to FSH, encouraging the development of one or more dominant follicles and preparing the ovary for ovulation.
Standard Protocols for Timing and Dosing
Timing Protocols
Letrozole is typically taken for a short duration of five consecutive days within the early part of the menstrual cycle. The timing of the first dose is calculated from the start of a patient’s period, with Day 1 being the first day of full menstrual flow. The two most common protocols involve starting the medication on either Cycle Day 3 (Day 3 through Day 7 regimen) or Cycle Day 5 (Day 5 through Day 9 protocol). The Cycle Day 3 regimen is often chosen to recruit follicles earlier, while the Cycle Day 5 protocol may be selected for a slower or more controlled growth. The physician determines the starting day based on the patient’s specific diagnosis and prior treatment response.
Dosage and Administration
The standard starting dosage is generally 2.5 milligrams (mg) or 5 mg taken once daily. If a patient does not ovulate or achieve sufficient follicle growth at the initial dose, the physician may increase it in subsequent cycles to 7.5 mg. It is important to take the pill at the same time each day to maintain consistent medication levels in the bloodstream. If a dose is missed, the patient should contact their healthcare provider immediately for personalized guidance, rather than attempting to double the next dose.
Monitoring After the Treatment Course
Once the five-day course of Letrozole is complete, the focus shifts to monitoring the ovarian response to the medication. Ovulation typically occurs approximately five to ten days after the last pill is taken, often falling between Cycle Day 14 and Cycle Day 19. Monitoring is necessary to accurately time intercourse or intrauterine insemination (IUI).
Monitoring is commonly performed using transvaginal ultrasound, which allows the physician to directly measure the size and number of growing follicles. A follicle is generally considered mature and ready for release when it reaches a diameter between 16 and 20 millimeters. Blood tests are also utilized to measure hormone levels, such as estrogen and progesterone, to confirm the impending or actual occurrence of ovulation.
Once a dominant follicle is observed to be mature, an injection of Human Chorionic Gonadotropin (HCG), often called a “trigger shot,” may be administered. This injection mimics the natural surge of Luteinizing Hormone (LH) and forces the final maturation and release of the egg, usually within 36 hours. If a trigger shot is not used, patients may use Ovulation Predictor Kits (OPKs) at home to detect their natural LH surge. All steps must be closely managed by a fertility specialist.