I believe that Jaminet and most others misunderstand the physiologic response to low glucose, and the true meaning of low thyroid. Glucose scarcity (deficiency may be a misnomer) elicits an evolutionary response to perceived low fuel availability. This results in a shift in genetic expression to allow that organism to better survive the perceived famine. Intracellular antioxidant systems, heat shock proteins, DNA repair, autophagy, all tricks that nature has, are up-regulated to allow the organism to increase repair and maintain itself to remain healthy and alive. As part of this genetic expression, and as part and parcel of nature’s mechanism to allow the maintenance of health and actually reduce the rate of aging, certain events will take place as seen in caloric restricted animals. These include a reduction in serum glucose, insulin, leptin, and free T3.
The reduction in free T3 is of great benefit, reducing temperature, metabolic damage and decreasing catabolism. TSH is not elevated. We are not talking about a hypothyroid condition. It is a purposeful reduction in thyroid activity to elicit health. Yes, reverse T3 is increased, as this is a normal, healthy, physiologic mechanism to reduce thyroid activity. It is not always a sign of malfunctioning thyroid as is frequently taught, but is instead one of the redundant ways that thyroid action is controlled. Reduced thyroid level in this regard is analogous to reduced fasting insulin that generally indicates improved insulin sensitivity, which also occurs in fasting and caloric restricted animals, and is also part and parcel of the benefits seen. Sometimes our complexity is indeed paradoxical.