DaveFoster
Member
In their 2017 study, Celi and others studied the effects of liothyronine (T3) in the treatment of hypothyroidism, and they found that a 0.34 ratio of T3 to T4 resulted in a euthyroid state. For reference, this would be something like 34 mcg of T3 for every 100 mcg of T4, which matches exactly the ratio that Dr. Peat recommends in his article, Thyroid: Therapies, Confusion, and Fraud.
Relevant excerpts from either written piece lie below.
Relevant excerpts from either written piece lie below.
Celi and others said:...we systematically assessed the differences in the targets of the TH action, measured at a clamped, euthyroid state in the pituitary. The 0.34 ± 0.05 μg/μg ratio of l-T3/l-T4 daily dose is in agreement with previous estimates obtained by compartmental analysis (29). Although the mean serum T3 level remained within the normal range, l-T3 treatment resulted in significantly higher T3 serum concentrations. This is not surprising because type-2 deiodinase (30) is particularly active in the thyrotroph, and it is thought to play a major role in the hypothalamus-pituitary-thyroid axis (27, 31). Hence, this axis is probably more responsive to the inhibitory effects of T4 than T3.
Raymond Peat said:The brain concentrates T3 from the serum, and may have a concentration 6 times higher than the serum (Goumaz, et al., 1987), and it can achieve a higher concentration of T3 than T4. It takes up and concentrates T3, while tending to expel T4. Reverse T3 (rT3) doesn't have much ability to enter the brain, but increased T4 can cause it to be produced in the brain. These observations suggest to me that the blood's T3:T4 ratio would be very "brain favorable" if it approached more closely to the ratio formed in the thyroid gland, and secreted into the blood. Although most synthetic combination thyroid products now use a ratio of four T4 to one T3, many people feel that their memory and thinking are clearer when they take a ratio of about three to one. More active metabolism probably keeps the blood ratio of T3 to T4 relatively high, with the liver consuming T4 at about the same rate that T3 is used.