Saturday, December 17, 2011

Clomid and Letrozole Part 2

Now a bit more about Letrozol (also known as Femara). Letrozol and Clomid have the same end result: ovulation, but they go about it in a much different way. Letrozol acts by decreasing the body’s ability to make estrogen, whereas with Clomid estrogen is produced but its actions are blocked.

Letrozol is an aromatase inhibitor. Aromatase is the enzyme that makes estrogen. Now there are many steps to making estrogen, but aromatase is the last and most important step. Aromatase takes testosterone and slightly changes it to become estrogen. Yes, women have some testosterone, but men have more. To me it’s amazing that testosterone and estrogen, two hormones that are so different, are just one step away from each other. Nevertheless, that’s the case and the system somehow works.

As Letrazol inhibits the formation of estrogen, estrogen levels fall. And this helps women become pregnant? Crazy as it sounds that answer is yes, and this happens in a way similar to the workings of Clomid. Once again, the brain sees no estrogen (this time because there really is very little). The brain reacts, and puts out more FSH to stimulate the ovary to make estrogen, which the ovary can only do my making a follicle, that just so happens to contain an egg. Just as with the Clomid, the follicle grows, the egg matures and ovulation usually comes next.

How can you get pregnant if you are taking a drug that is blocking (Clomid) or eliminating (Letrozol) estrogen? You do not need estrogen to ovulate. Estrogen is a buy-product of the growing follicle. The reason estrogen is made by the follicle is so that the lining of the uterus (the endometirum) can grow. And yes you need the endometrium, but for most women only a small amount of estrogen is needed to get a good lining. Plus, the aromatase inhibitors do not make the estrogen go to zero, and Clomid does no completely block estrogen. These drugs may cause the endometrium to see much less estrogen than usual but enough gets through for adequate growth.

In addition, Letrazol and Clomid are only taken for 5 days, usually until day 7-9. This leaves 5-6 days for the follicle to grow a bit more and produce more estrogen, all while the drugs are leaving the body.

There are some differences in the negative effects between Clomid and Letrozol. Clomid has a long half life meaning it stays in the body for days after the last dose. Its half life is 5-7 days, so blood levels go up and up each day the pill is taken and significant amounts are present around ovulation. Therefore conditions around the time of ovulation can be effected by the Clomid i.e. the cervical mucus can be too thick and the lining of the uterus can be too thin. The half life of Letrozol is shorter.

The good news is that for most women these drugs work quite well. We do not know why some women have more side effects than others. Subtle genetic differences between women lead to very subtle differences in the shapes of one or more of the proteins involved in binding.

Letrozol also has fewer mental side effects. Common Clomid side effects include headaches, hot flashes, depression, seeing spots, jitteriness, trouble sleeping, and there are a few others. Letrozol does not cause as many of these symptoms.

If Letrozol seems to be better for the mucus, lining of the uterus, and has fewer side effects, why don’t we use it as our first line of therapy over Clomid? This requires a little more discussion which will come in the next entry.

Thanks for reading and don’t forget the disclaimer 5.17.06.

Dr. Licciardi

32 comments:

  1. Thanks for sharing this information. I don't respond to Clomid, so I will be trying Femara during my next cycle.

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  2. I had the vision issues and hot flashes with clomid. femara was much easier, but my legs would really ache while I was taking it. Any ideas why?

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  3. I just recently found your blog and really enjoy it. I just started taking Clomid and am having some interesting side effects with it. It helps to learn more about how it is working in my body to produce results. Thank you!

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  4. Thank you for your blog! I am on my 3rd round of Letrozole and will have my 3rd IUI soon. I like the information your giving us! If this one doesn't work I am thinking of asking to switch to Clomid because I am not growing nice and big folicles on the Letrozole.

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  5. Hi I heard that Clomid can increase the size of fibroids. How about Letrozole? I have 2 fibroids of about 6 cm with no symptoms and my Dr told me they would not affect my ttc. However I still can't get pregnant. So DH & I are meeting with RE for our 1st consultation next Tue. I'm looking for more info about my situation or anything related. I wonder if Letrozole is more beneficial and help me get pregnant easier than Clomid( considering the side-effects it might have on fibroids)?

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  6. Thank you so much for your blog! I am on month 4 of Clomid (PCOS) after an ectopic in July. Would it be unreasonable to be checked for Endemetriosis? I'm a little puzzled as to why it hasnt been already as I've already voiced concern about it.

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  7. Blair5:50 PM

    Hello. At age 29, how bad is an FSH level of 18 on day 3 and then a level of 17 on day 10?? I just completed my first iui which was unsuccessful and will be returning to my doctor's office for genetic/ chromosomal blood tests - I'm very worried! My understanding is that iui and I've may not be successful with these levels?

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  8. I am not a doctor and got worried after my wife had been placed on clomid for about 5 times. Check out http://www.iwanttogetpregnantnow.net

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  9. Anonymous2:13 PM

    Great information! I was in a clinical trial for Femara vs Clomid (PPCOS II), and was pregnant in the 2nd round (no idea which drug, though). It's nice to know more about the 2 drugs I may have been on.

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  10. Anonymous1:11 PM

    Hi Doctor! Thanks for this blog its been very helpful. After five years of trying on our own, I started getting tested, since I turned 30. My dr. told me I do not ovulate every month, my prog. levels were 2.3. After one round of clomid 50mg, I was supposed to meet with my dr. to follow up. This was over the holidays, and he went out of town for two weeks. I started my period over that time, and called another dr. about my 2nd round of Clomid, she said to double it, so I took 100mg, since I did not respond well on 50mg. I called his office to check in and see when they were going to monitor me this month, and was told the dr. refuses to see me until after this cycle is over and will not set up any blood work. I felt like I was being punished. Is this normal? What should I do? Clomid needs to be monitored.

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  11. Marigold5:27 PM

    Hi Dr,
    I'm 29 and doing my first IVF after 3 failed IUIs. I used to have irregular periods and some symptoms of PCOS as well as an elevated TSH for which I'm taking 75mcg of synthroid every day. Anyway, ER was yesterday and they retrieved 20 eggs, 17 were mature, 11 fertilized. What odds of success do you give me? And should I be worried about TSH levels causing a miscarriage if I do get pregnant? Thanks so much!!

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  12. Chinese medicine has some solutions for infertility as well.
    FYI http://truthaboutquickness.org/recommends/Pregnancy_Miracle

    ReplyDelete
  13. Interesting information! Thanks for sharing!
    Cathie
    www.walkinginhisplan.blogspot.com

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  14. Anonymous7:04 AM

    I stumbled onto your blog while researching infertility and I am so thankful! You are understandably probably very busy and you still take the time out to provide a blog to discuss issues and answer questions. Thank you so much! I'm currently on my 3rd round of letrozole after multiple rounds of clomid produced no mature follicles. (PCOS) So far I've only ovulated once on 10mg, but very hopeful that I will again.

    Again, thank you!

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  19. Hi,

    As part of my dissertation I am researching the relationship between infertility, depression and body image in women, specifically as related to the differences between women with primary (unable to conceive and maintain a first pregnancy) and secondary (unable to conceive and maintain a pregnancy subsequent to having at least one child) infertility. I hope that findings from this study will eventually help develop better psychotherapy treatments for women with infertility.

    Females between the ages of 18-50, who are currently infertile (have had unprotected sex for at least 12 months with no successful pregnancy), and have no adopted/step child(ren) are eligible to participate in this study. The study entails completing questionnaires either online (https://www.surveymonkey.com/s/YCBQ35D), or by hard-copy upon request (call: 347-766-3798), and may be completed in 20-30 minutes. Participation is voluntary and confidentiality will be maintained. For each person who completes the survey, 2$ will be donated to RESOLVE: The National Infertility Association. This study has been approved by the FDU IRB (2/17/12).

    Feel free to contact me with any further questions about this study. I may be reached at 347-766-3798 or michalm@student.fdu.edu.

    Thank you for your time and consideration.

    Michal Munk, M.A.
    Clinical Psychology
    Fairleigh Dickinson University

    ReplyDelete
  20. Hi,

    As part of my dissertation I am researching the relationship between infertility, depression and body image in women, specifically as related to the differences between women with primary (unable to conceive and maintain a first pregnancy) and secondary (unable to conceive and maintain a pregnancy subsequent to having at least one child) infertility. I hope that findings from this study will eventually help develop better psychotherapy treatments for women with infertility.

    Females between the ages of 18-50, who are currently infertile (have had unprotected sex for at least 12 months with no successful pregnancy), and have no adopted/step child(ren) are eligible to participate in this study. The study entails completing questionnaires either online (https://www.surveymonkey.com/s/YCBQ35D), or by hard-copy upon request (call: 347-766-3798), and may be completed in 20-30 minutes. Participation is voluntary and confidentiality will be maintained. For each person who completes the survey, 2$ will be donated to RESOLVE: The National Infertility Association. This study has been approved by the FDU IRB (2/17/12).

    Feel free to contact me with any further questions about this study. I may be reached at 347-766-3798 or michalm@student.fdu.edu.

    Thank you for your time and consideration.

    Michal Munk, M.A.
    Clinical Psychology
    Fairleigh Dickinson University

    ReplyDelete
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