levothyroxine and tsh levels

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I want to know if there's a chart that that shows different levels of TSH and the dose of levothyroxine required for treatment.

Is there such a thing?

 

I'm not familiar with dosing levothyroxine directly off of TSH levels. I am more familiar with looking at patient characteristics, such as if the patient has not yet started puberty, >50 years old, or if the patient has cardiac disease (to name a few). For example, in a healthy patient <50 years old with hypothyroidism, you could consider a starting dose of 50-100 mcg and then titrate every 6-8 weeks based on lab parameters and clinical response. Older or sicker patients may require lower doses and slower titrations.

 

Dosing levothyroxine is a b*tch. If I got asked by a doctor how to dose it I would just tell them its a b*tch. It has a long half-life, has no reliable dose-response since it affects a hormone, and is always complicated by subjective patient experience that may or may not be related to the current dose of the drug. Canned response: Consult an endocrinologist.

 

Levothyroxine dosing is complicated. There are too many variables for there to be a simple chart to predict the appropriate dosage.

 

However, Primary Care docs always ask how to prescribe the fraction doses such as 88ug, 112ug, etc.
So I was thinking if there's a chart that can tell you this (with underlying symptoms, ofcourse), for example:

TSH: x-y ---> levothyroxine 25ug
TSH: a-b ---> levothyroxine 88ug

 

it doesn't work like that. a certain amount of levothyroxine doesn't raise tsh up a certain number of point. its very patient specificic. a dose of 50 might increase the tsh the same amount as a dose of 150 in another person.

also you don't only go by levels, but you go by the way the patient looks and feels, because that is the whole point of treating hypothyroidism.

 

Can anyone point me to a credible source showing a guide/flowchart of the treatment?

 

There is no chart to my knowledge. It all varies from patient to patient. Generally, older patients start at 25 and younger at 50. It was mentioned before, you treat the patient and not the number.

 

According to Cecil Medicine, the optimal dose of thyroxine for replacement is 1.8 ug/kg of lean body mass, 1.0 ug/kg in the elderly d/t reduced metabolism. You measure the TSH in 4-6 wks to target 1.0-2.0 mIU/L. You can give the full dose in otherwise healthly adults, but start with tiny doses and titrate upwards if the pt has CAD or long-standing hypothyroidism.

There's no such thing as dosing according to TSH; it's messier than that. And there's a psychological component with these pts - I recall one of my coworkers who slept over at work because of a snowstorm. He came to the medical unit claiming symptoms of hypothyroidism because three hours had elapsed since the time he usually took his Synthroid.

 

What every one else said. Dosing is very patient specific. Not to mention there are also a subset of patients who will have a normal TSH, but low T4 (usually because of adrenal problems)....so their dosing would have nothing to do with their TSH. There is also the subset of patients that have low T4 and low T3 and may need something else besides levothyroxine. So yeah, basically doctors just pick a dose to start with, then titrate up or down based on labs & patient response.

 

For the life of me I can't figure out how some of these patients end up on regimens like 88mcg MWF, 75mcg TRSa, 112mcg Sun. I mean, what the heck kind of titration are you doing that ends up that way? I know warfarin you're using a percentage of weekly dose so that can happen, but I've never heard of how to go about it for levothyroxine.

 

Adrenal problems, what's that about? Haven't heard that before, I've always thought those people were supposed to just have early hashimoto's thyroiditis that may or may not progress to the full picture.

 

Studies right now say that the average maintenance dose for an adult patient is about 125 mcg/day. Typically, for a patient without cardiac disease, you're supposed to start at 50 mcg/day and titrate up to 100 after a month. After that, go partially off TSH and partially off how the patient feels. If they report feeling like their heart is racing, etc, you might drop it to 88 to see what happens. In thyroid meds, a little goes a LONG way.

 

If a patient has low T4, won't you obviously have low T3? I'm not sure I get what you're saying.

 

I always assumed their levels were out of whack because they couldn't keep their goofy medication schedule straight, so the doctor kept making minute changes on their medicine, creating a never-ending cycle. Seriously, being young & healthy, I would have problems keeping some of these 3 or 4 day cycle they come up with straight. I don't know how doctors expect some of these elderly patients to do it.

I'm not really sure how it works, but I've heard from a few patients and more than one doctor that they became mildly/moderately hypothyroid after suddenly stopping/weaning off too fast of steroids. They had normal TSH, but low T4. In at least 1 case the person seemingly recovered after a few years, and no longer needed thyroid replacement.

Not always. Many people with mild/moderate hypothyrodism will have high TSH, low T4, but normal T3 (which is why many doctors don't even check the T3 unless the patient has failed to respond to standard therapy.)