Hormones, hormones, hormones…why am I injecting all these hormones and what do they do?? This is a good question – apart from doing as I am told by the doctor, I thought I should be able to at least answer this question to my friends and family who ask: What does each drug do and why I am taking it? So I am going to have to go back to school with this, I hope I am not patronising. I am sure I could recant all of this from my biology classes if they weren’t almost 20 years ago!!!
There are several ways a doctor can choose to stimulate ovaries for IVF treatment, these are called protocols and they can vary in dosage, type and timings. My doctor has chosen the antagonist protocol for me.
Back to basics...so let’s take it back to school…there are four major hormones involved in the menstrual cycle: FSH (Follicle-Stimulating Hormone), LH (Luteinizing Hormone), Estrogen and Progesterone. Today I am going to focus only on the first two weeks of the menstrual cycle, also known as the follicular phase.
During the folliclar phase, in a normal menstrual cycle the following events occur:
- FSH and LH are released from the brain and travel into the blood to the ovaries.
- These hormones stimulate 15-20 eggs in the ovaries, each in its own “shell”, called a follicle.
- These hormones (FSH and LH) also trigger an increase in the production of estrogen.
- As estrogen levels rise, like a switch, it turns off the production of FSH. This careful balance of hormones allows the body to limit the number of follicles that mature to just one.
So what does this mean for IVF? The goal of IVF is to produce as many mature eggs as possible to create conditions for the greatest chance of successful conception, to do this doctors use injectible hormones to control this phase of the mentrual cycle and stimulate the growth and maturation of the eggs, ready to be fertilised.
So we know that FSH stimulates the growth and number of small follicles, for small follicles FSH is the major survival factor that enables them to develop beyond 5mm in diameter and to avoid apoptosis, i.e. the programmed death of a follicle and egg. In a normal menstrual cycle, multiple small follicles produce inhibin-B to lower FSH levels so that only one follicle will mature. In an IVF cycle, artificially increased FSH overides the inhibin-B levels and therefore allows multiple follicles to grow and mature. This is where the drugs Gonal-F and Menopur come in.
Gonal-F is a follitropin alpha medication (also known as a gonadotropin). It is a synthetic version of the naturally-occurring FSH. Where as, Menopur (also a gonadotropin), a combination of both FSH and LH, however unlike Gonal-F, Menopur is natural; it is extracted and purified from the urine of post-menopausal women -ummmm nice. It is believed that a small quantity of LH during ovarian stimulation produces a better result in some patients. It is for this reason that my doctor prescribes a combination of the natural and synthetic combination of gonadotropins, menopur and gonal-f.
As the gonal-F and menopur start to work, we need to make sure ovulation doesn’t occur prematurely, therefore they use the injectible Cetrotide. The active substance in cetrotide is cetrorelix, this blocks the natural hormone LHRH (Lutenising hormone releasing hormone). LHRH controls the production and release of LH which causes ovulation. The cetrotide stops the production of LH, preventing premature ovulation. This allows the doctors to carefully control when ovulation will occur.
The trigger injection. The controlled hormonal stimulation I have described so far usually lasts for about 8-12 days, and dosages vary depending on how the woman responds to the drugs. This happens all before another drug is injected – Ovidrel. Ovidrel is the trigger injection containing a synthetic form of the hormone human chorionic gonadotropin – hCG. There are several brand names for the hCG trigger shot including Ovidrel, Profasi, Pregnyl, and Novarel. hCG is known as the pregnancy hormone, but it also happens to be molecularly similar to LH. In a natural cycle, LH triggers ovulation. As part of fertility treatment, an injection of hCG is used to trigger the maturation of eggs. Ovulation usually occurs 36 hours after this trigger injection is given. In the case of IVF, egg retrieval is carefully timed to collect the eggs just before ovulation, but long enough that the eggs have matured in the body ready to be extracted for fertilisation.
In part 3 I will focus on explaining the second phase of the menstrual cycle which includes the lovely hormones estrogen and progesterone….yippeeee!!!