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Just the Facts, Ma’am: Letrozole

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Dr. Randall A. Loy breaks down the differences between Clomiphene and Letrozole with his usual wit and wisdom. Although he admits he’s not an artist, you’ll have no problem following his pictorial of just how these fertility drugs work in a woman’s body. Informative and inspirational…this episode is absolutely Dr. Loy at his best!

Hi my name is randall loy and you found us on the infertility channel thanks so much for joining us i’m appreciative they’re here we’re going to actually start with a question this is from ellen from florence montana not florence italy ellen asks have been unquote for three cycles now my doctor has recommended for mara i’ve heard that foam are immense aif what

Do you think great question elle and i’d like to talk to you about that for a few minutes and i’m going to use this little drawing over here to help make that more understandable now tomorrow is the trade name for letrozole letrozole is a third generation so called aromatase inhibitor and we’ve talked about this in previous episodes but let me just refresh your

Memory aromatisse is an enzyme that converts male hormones androgens into female hormones estrogens and that happens in the ovary now aromatisse is found not only in the ovary but it’s found in the testes the brain and the fat so it’s possible for all of those organs and others really to be able to convert androgens and estrogens so typically hamara or letrozole is

Prescribed for about three to five cycle days per month it can be prescribed even longer but letrozole is a pill and it starts at two point five milligrams goes up to seven point five or even ten milligrams per day and it is very effective in getting absorbed rapidly and shutting off these aroma taste enzymes now specifically with respect to the ovary i’m going to

Blow this up a little bit so the ovary usually makes one dominant follicle per month it’s an egg containing cysts and around the periphery and i’ll think about this three dimensionally and please forgive my terrible drawings so these granulosa cells nourish that egg cell and it turns out that androgens like testosterone and androstenone are made by the theca cells

Outside of the follicle and the granulosa cells have the aroma taste enzyme so what happens is that testosterone is typically converted into the most potent estrogen called estradiol and andrew steamed ione is converted into one that’s not quite as strong called esther own and both of these androgens can be interconverted as can the estrogens but what happens is

When you take these pills for three four five days a month they act on the enzyme system in the granulosa cells and they shut off this reaction so what happens is that there is less in the way of estrogen feeding back to the pituitary into the hypothalamus now i know what you’re thinking this is not a scrotum and a poorly endowed person here it’s actually this

Is the optic chiasm it’s the nerve where the optic nerve kind of crosses be behind the eyes and in front of the pituitary gland this is the front of the pituitary the back of the pituitary and this is the hypothalamus here so very very critical obviously for ovulation so what happens is that the lower estrogen level by aroma taste causes the from the pituitary to

Increase its follicle stimulating hormone and that goes down and causes these cells to proliferate and nourish that egg better so that’s the way letrozole works it’s very very safe it has a half-life a terminal half-life of around 42 hours which practically means by the time of that embryo reaches your uterus it is out of your body in ellen speaking of the safety

Of this doctor tell andy togas to land in montreal at mcgill back in 2006 looked at 911 patients who had been exposed to for mara and dr. tal andy found that the birth defect rate or genetic problems with hamara were 2.4 percent and with clomid they were 4.8% so exactly 1/2 now let’s talk a little bit about clomid and its mechanism now clomid as you know is it’s

An old medication it’s been around for 50 years it’s a so-called selective estrogen receptor modulators or a cern but terms actually effect estrogen receptors so we know that clomid is a weak estrogen it’s a weak anti estrogen and it binds estrogen receptor sites up here in the hypothalamus so it basically imposes a blockade on the hypothalamus now different from

Letrozole we have a normal amount of estrogen feeding back to the pituitary and hypothalamus but as you can see there’s that block clomid has blocked out the estrogen so the brain thinks hey – elestra jin – glass surgeon and red lights go off in the pituitary and hypothalamus and so it does the only thing it knows how to do once again in response to this blockade

More fsh is elaborated which goes down and will increase those granulosa cells and in clomid it tends to increase or has a possibility of increasing even another follicle so whereas with letrozole the twin rate is less than 1% with clomid it is around 7 or 8% so in many ways we feel that letrozole may be the drug of choice so late last year at our annual meeting

The american society of reproductive medicine meeting there was a great paper from the national institutes of health that suggested that letrozole was even more efficacious in polycystic ovarian syndrome patients and clomid and they recommended in that abstract that letrozole become the first line of therapy for patients with pcos over the last several years there

Have been several studies including systematic reviews and meta-analyses compilations of studies which have suggested that letrozole is at least as effective in inducing ovulation as clomid so for the past 14 years or so we’ve been using letrozole as a primary drug one more word ellen about efficacy and this comes back to a statement by the makers of tomorrow

Novartis as the pharmaceutical company back in 2005 they issued a statement that ferrara is contraindicated not indicated in women who are going to become pregnant are pregnant or breastfeeding because there could be birth defects associated so ellen thanks once again for that question i do believe that letrozole is safe once again because it’s out of your system

By the time that the embryo gets into your uterus we believe it is the drug for 2014 the first-line therapy and it’s probably going to be the drug for the foreseeable future now one last thing i am not an artist i only try to play one on youtube so please forgive the graphic images today thanks so much for joining me today be sure to share this video with your

Friends and subscribe to catch all-new episodes each week here on the infertility channel plus follow us on facebook and twitter i love hearing from you comment below or tell me what you want to see on future episodes by sending me an email to comments at infertility channel org until next week

Transcribed from video
Just the Facts, Ma'am: Letrozole By InfertilityChannel