General Synthroid Questions And Side Effects

Our pharmacist answers the latest questions regarding the thyroid drug, Synthroid.

Sep 25, 2017

John asked

Part 1: Hi I started taking synthroid for my hypothyroidsim about 2 weeks ago and I had a few questions. I'm currently taking 75mcg and I know I'm supposed to take it on an empty stomach but I was wondering when I could have my first meal if I take the medication at 9am every morning. I've been having breakfast at 12pm so that gives my body 3 hours to completely absorb the medication, but I'm thinking this might be unnecessary. Also, about a week after I started the medication I've been experiencing pretty significant abdominal bloating. At about the one week mark I gained 4 pounds overnight and it's remained that way since then... my caloric intake has remained exactly the same so it has to be from the medication. Is this a common side effect? Or perhaps it could be my body getting used to the synthroid? Any information regarding my questions will be greatly appreciated. ​
Part 2: I did have two more question though, do you know if there is any correlation between the synthroid medication and libido? About the same time that I noticed the abdominal bloating, I also noticed a decrease in my sex drive, and like the bloating, it's been that way since. I'm a 20 year old male, 164 pounds, and about 5'8, and I've never had this happen to me. I used to always get random erections throughout the day, especially in the morning, but for the last week I haven't even had one. And my last question, for the past few days it seems like I've been pretty short of breath. I have to constantly take deep breaths, and I'm wondering if this is a possible side effect also. I'm hoping all of this is just my body getting used to the new levels of thyroid hormone. I was planning on asking all of these questions to my endocrinologist in a few weeks as well, but I didn't want to seem like a difficult patient going into my next appointment with all of these issues, so I'd like to possibly clear some of this up before then.

Answer

Part 1

In terms of when to take the medication, the most important thing is consistency. The dosage of thyroid medications are extremely small and a small change in absorption in your body can cause some major effects. Food generally affects both the rate and extent of how drugs are absorbed. Taking the medication with food one day, and not with food the next day, can cause fluctuations in the dose you are actually absorbing in your body. Synthroid (levothyroxine) dosages are measure in micrograms. One microgram is 1/1000 of 1 mg. That's a really small dose! The different dosages of the medication are only separated in some cases by as little as 12 mcg, so we can see a small change can make a big difference.

The general recommendation is to take the medication with a full glass of water, 30 minutes before food. This allows for optimal and consistent absorption. You do not need to wait longer than that. The goal is for the medication to get to the small intestine to begin absorption. Taking it with food delays how the medication is released from the stomach, and that is what causes the changes in absorption. Now, having said that, I do see many patients that take the medication with food and get the desired results. Again,the most important thing is consistency. If you take your Synthroid with an egg for breakfast every morning, that is fine. Your body will get used to that method of administration.

In terms of the side effect you are experiencing, it usually is not common to have many problems from the medication. Side effects with it are usually attributed to either allergies/sensitivities to the ingredients in the medication or to an inadequate dose (either still being too low and causing the symptoms of hypothyroidism or too high and causing the symptoms of hyperthyroidism). I always like to say in an ideal world,there wouldn't be any side effects because we are really just trying to replace a deficiency of thyroid hormone in the body.

To be honest, the only time I have ever heard of bloating on the medication is when there was a problem with one of the actual ingredients (an inactive ingredient) in the medication or if there is a problem with the fact that the Synthroid medication is only a T4 drug (see our website guide for more information on the hormones contained in thyroid drugs). Weight gain usually only occurs when the thyroid is too low, but overnight would be much to fast for that to be the cause. There could be other factors at play, or as you mentioned, you might be sensitive to some part of the medication and just have to get used to it. If you have recurring problems with it, I would possibly recommend switching to either a different generic manufacturer of levothyroxine, taking the brand name Synthroid, or trying another thyroid type drug such as Cytomel or Armour Thyroid. Sometimes patients have better success on drugs like Cytomel or Armour Thyroid for various reasons, so it may be worth a shot if things don't get better.

If you haven't already, I recommend looking at our hypothyroidism guide on our webpage:

/hypothyroidism-guide.html

It has a lot of good information in it!

Part 2

Thyroid dysfunction and thyroid medication isn't typically associated with libido dysfunction and erectile dysfunction. They aren't known as the classic symptoms of thyroid problems. Having said that, the actions of the thyroid hormones are extremely complex and far reaching. They influence everything from growth and development to various cardiovascular effects.

Low thyroid hormone specifically is associated with slow heart rate, a decrease in cardiac index (a measurement of heart performance) and increased vascular resistance. The increased vascular resistance (think of this as resistance to blood flow) can certainly cause some sort of sexual dysfunction. Sexual side effects aren't typically associated with thyroid dysfunction as mentioned previously, but problems with the thyroid most certainly could cause some issues so there is certainly a possibility the problems you mentioned could be due to your thyroid problems. Your endocrinologist I'm sure can give you much more information.

 

In my experience I have not had a patient mention to me shortness of breath but it makes sense to me in terms of having hypothyroidism. You do mention that it really only started happening after taking the

medication however so honestly I'm not too sure on this one. The cardiovascular effects of hypothyroidism and the decrease in cardiac output can certainly cause issues with feeling short of breath. In terms of the medications, I do know that when you increase thyroid levels the body usually by increasing oxygen consumption (how much oxygen your body uses).  I don't know if this would really contribute to shortness of breath. I do apologize I don't have as much information for you on this one...

 

I have full confidence that over time your side effects will get better and the effects of thyroid dysfunction gets less and less. It's all about finding the right dose, the right medication and just correcting an abnormality with the levels of thyroid in your body. It can just take some time and tinkering to get everything right.

 

I wish you the best of luck in the future and I'm sure your endocrinologist can answer all of your questions for you!

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