So I just want to share what happened to me when I took Letrozole - in case there is anyone else like me! I was put on 2.5mg of Letrozole CD 5-9 by my OBGYN for late ovulation issues (irregular cycles). TTC 2 years, no other issues either side & normal bloodwork. This was the lowest dose of Letrozole so I was super hopeful about it! I started taking my first round in Oct 2019. I never noticed any sort of side effects on the days I took the pills, even when I took them in the morning. A week later I began getting headaches & then an extreme migraine on Oct 16th. I think it was 5dpo. Medicine wasn’t working, I was too weak to stand to even go to the doctor but somehow pushed myself through the nausea. This migraine felt like the one I had with a sinus infection 2 years ago - my head & face hurt, except it was only the left side. Urgent care said my left nasal passage was inflamed but that it wasn’t a sinus infection. So they sent me to the ER where I had a CT scan and was given Benadryl & then sent home with normal CT scan results. My sinus/face/head was still hurting so much every single day and it was “inflamed”- I couldn’t do anything but lay down (anyone had a sinus infection before? - worst pain ever). I went from one doctors appointment to another. ENT said to go to neurologist. Neurologist couldn’t figure it out. I was told to go to the allergist. There I was going weekly & given allergy medicine for 2 months (nasal steroid sprays, saline rinses, and antihistamines) as they thought my body was “mimicking” something in the environment and causing an allergic reaction. Each allergy medication needed time to work they said. Had an MRI & MRA with neurologist, too. Normal. No aneurysms. My headaches would often grow into migraines and I was in & out of so so many doctors & urgent cares. Took Tylenol every day to manage the pain (not allowed to take ibuprofen when TTC so pain relievers are limited), and just to be able to function to leave the house. Four months of this later and lots of prayers begging the Lord for help, and I saw a 2nd ENT. He diagnosed me right away with cluster headaches caused by hormones from this hormone medication. Honestly I was shocked. This doctor said the blood vessels in my head have been constricted and closed my left nasal passage. It was so constricted that the inside of my nose was white! (No blood supply). My thyroid was enlarged from it too he said. Did ultrasound & bloodwork on thyroid - all normal. Anytime I had researched Letrozole, most people had “side effects” ONLY on the days they took the pills. That’s not the rule & it’s not everyone. After this happened, I began researching more and noticed other women who had said they had the “worst headache of their life” during Letrozole & had to get off it, etc etc. Many of them said they were already migraine-prone people, which I am! I actually usually get hormonal migraines once a month around my menstrual. This was Not that. I can usually handle my usual migraines, this was so much worse. There was eye pain, ear pain, face pain, & in my head. This ENT said I had so much pressure on my Eustachian tubes in my ears. But it wasn’t sinuses and all my imaging was clear. There was not one day of relief in those near four months (4 rounds of Letrozole). My OBGYN didn’t know by the way because I told him “I developed allergies it appears” & he didn’t think anything of it. Neither did I. I told him I was taking sinus pain medication. My neurologist halfway through this trial had me stop taking any more Tylenol for fear of liver damage since I was taking it every single day. I was so happy when my period would arrive so that I could get some sort of medication pain relief! A month later my liver was tested and yes the numbers are now elevated so I am fortunate to have a doctor at least who made me stop taking even a low dose of Tylenol.

Anyway, it’s been a bit traumatizing 4 months. I hope others who take this medicine that their doctors give them, that if they begin experiencing strange things going on with their body, that they would be able to look up other cases of side effects, at least here if not elsewhere, & see that they’re not the only ones! And I hope they tell their OBGYN about everything. I wish I had. I feel so foolish that I never related the two (neither did any doctors! They were literally all giving me medications that cause more vasoconstriction such as antihistamines, nasal decongestants, triptans, etc!). Honestly I had thought I was “getting sick” right before I started my first round of Letrozole and thought this was indeed now a sinus infection, or at least environmental allergies. I’m off the Letrozole and 2 wks into my next cycle now medication-free and honestly I do feel SO much better but still have some lasting effects (mild headaches and the ear and eye pain/redness is still there). I’ve been labeled by doctors “sensitive to medicine”. Definitely. So many worst things could’ve happened during this time and I’m so grateful it didn’t! Though, it is hard having a headache/migraine every day. I did read about RCVS condition and how it happens in women who are more migraine-prone, typically vasoconstriction in their head happening during pregnancy or post-partum when hormones drastically change. Or any change in their birth control or hormonal medicine. Vasoconstriction is pretty serious - obviously bad cases can lead to stroke and tons of other issues. I have borderline eye pressure now and that could’ve turned into glaucoma from all the nasal steroids or whatever else I was on. On the other hand, my cycles were great on Letrozole and my body responded to 2.5mg and ovulation was normal around CD14, 15, and 16 on those 4 cycles. But it was not worth it. Sadly my body could not handle having my hormones regulated. The doctors never did figure out why my body or blood vessels reacted this way. I did try fertility herbal tea to try & regulate my hormones since herbs are more gentle on your body, but I began experiencing the ear pain again so I stopped that too. I’m not sure if I’m giving up too easily, but this was scary for us, & if this is how my body is going to react when my hormones fluctuate or “normalize”, we may look into adopting instead. Honestly we have stopped TTC, focusing on getting healthy again and getting my liver back to healthy normal. This is not to scare you but to spread awareness to those who know their bodies are sensitive - I am not the normal case!