Therefore, measuring the concentration of rT3 becomes meaningful (Ray Peat Clips, 2016a). A normal level is considered to be between 8-24 ng/dL (Mary Shomon, 2022). However, many thyroid specialists suggest that an optimal rT3 level should be at the lower end of this range. (Stop the thyroid Madness, 2023).

After consuming a balanced breakfast cortisol and adrenaline levels typically begin to normalize as blood sugar is sustained by food, instead of the stress hormones. This is an opportune time to measure both temperature and pulse rate, as it offers a clearer indication of thyroid function, free from the distortive effects of stress hormones (Peat,

As previously noted, the liver is the primary organ responsible for converting T4 to T3. Consequently, compromised liver function can lead to hypothyroidism (Peat, 2001a, p. 73).

A low resting pulse rate is recognized as a sign of hypothyroidism (Harward Medical School, 2023; Bhatt, 2020).

He noted that healthy individuals with good thyroid function usually have an average resting pulse rate of about 85 beats per minute, whereas those in less-than-optimal health often have rates around 70 beats per minute (Peat, 2008, p. 4).

The body is known to ramp up the production of rT3 during crisis situations such as critical illness, extreme dieting, or starvation (Mary Shomon, 2022; Alan Jacobs, 2023). Stress, and specifically the stress hormones adrenaline and cortisol, can increase the production of rT3 (Peat, 2008, p. 3; Ray Peat Clips, 2016a).

The T3 to rT3 ratio (T3/rT3) is useful in estimating the effective amount of T3 in the body. Ideally, this ratio should exceed 10, indicating significantly more T3 than rT3 in the blood (Alan Jacobs, 2023; Ray Peat Clips, 2016a).

Goitrogens can adversely affect thyroid health by hindering the thyroid gland’s ability to absorb iodine, an essential element for the synthesis of thyroid hormones (Cleveland Clinic, 2019).

Factors like a diet deficient in good quality protein and B-vitamins can also impair liver function,