FT3:FT4 ratio – Thyroid Patients Canada

Age, sex and TSH-FT4-FT3 relationships: Advanced lessons

August 4th, 2022thyroidpatientsca1 Comment

No one wants to be ageist or sexist in thyroid screening or diagnosis. But if we are blind to the way that age and sex can distort the hypothalamus-pituitary-thyroid (HPT) axis, our interpretations of thyroid hormone levels and TSH will inevitably become ageist and sexist by refusing to respect and accommodate human diversity. In a previous post, “Age bias may hide hypothyroidism under a normal TSH,” I discussed the transformations in TSH-FT4 relationships with age, focusing on adults. Then, I followed up with a post focusing on “Pediatric and teenage TSH, FT4, and FT3 levels.” Those previous posts discuss mainly …

An example of confusion about Free T3: Free T4 ratios

August 2nd, 2021thyroidpatientsca0 Comments

There’s a lot of confusion out there about Free T3: Free T4 ratios in bloodstream. Part of the confusion is about how these ratios are expressed in numbers and phrases. Should you express this ratio in blood as 1:4, 4:1 or 0.25, or 4.00? A second confusion may lead to a more substantial and harmful mistake. It is the idea that a scientific description is a prescription. Narrow descriptive findings in research, such as average FT3:FT4 ratios in a healthy-thyroid population, can easily be misapplied as prescriptive targets for thyroid therapy. But researchers understand the full range of diversity in …

Gullo: LT4 monotherapy and thyroid loss invert FT3 and FT4 per unit of TSH

November 12th, 2020thyroidpatientsca16 Comments

In 2011, Gullo’s research team published a landmark study in thyroid therapy titled “Levothyroxine Monotherapy Cannot Guarantee Euthyroidism in All Athyreotic Patients.” Gullo and colleagues examined the TSH, FT3 and FT4 levels and the FT3:FT4 ratios of 1,811 thyroidless patients on levothyroxine (LT4) monotherapy and compared them with 3,875 healthy controls. Gullo’s study shook the foundations of dogma by looking at distortions to thyroid hormone levels within the TSH reference range. It questioned the assumption that “euthyroid” status was achieved merely by normalizing TSH to the range of the thyroid-healthy population. Since it was published in 2011, the article has …

Normal FT3:FT4 thyroid hormone ratios in large populations

October 29th, 2020thyroidpatientsca5 Comments

A normal ratio of Free T3 (FT3) to Free T4 (FT4) thyroid hormones appears to be a basic principle in thyroid hormone economy when no thyroid hormone dosing and no disease interfere. In this post, I provide graphs, quotations, and discussions from Gullo, Strich, and Anderson as I present their FT3:FT4 ratio results, and I rely on science to present the mechanisms by which the ratio is adjusted in relationship to TSH in people not dosing thyroid hormones. Comparing across these 3 different studies, you’ll see how amazingly consistent population average FT3:FT4 ratios are among people with healthy thyroid glands …

Principles and Practical tips for Reverse T3, FT3, FT4

November 17th, 2019thyroidpatientsca8 Comments

This post follows up on several recent posts on the topic of Reverse T3 (RT3) and our thyroid hormone conversion enzymes, the three deiodinases. Here I’m providing some practical tips about Reverse T3 testing, test interpretation, and where we should be focusing our attention. In these posts, I aim to improve thyroid therapy by debunking myths about Reverse T3 hormone and replacing them with more complete understandings that can help us make wise therapy decisions together with our good scientific-minded thyroid doctors. In previous posts, I have proven that: Reverse T3 doesn’t actually have a role in “blocking” T3 from …