thyroid research - its fluctuation, and effects of exercise, circadian rhythm, meals , etc

It's recently been reported that my thyroid levels are below the normal threshold. So naturally I've taken an interest in investigating matters of "thyroid", and related.

Thyroid and Exercise Training

Most research appears to support the claim that thyroid is significantly influenced by exercise. Typically research indicates that the metabolic clearance rate of T4 increases with physical activity. This metabolic clearance is found in blood and in bodily tissues. The average increase in clearance rate is around 25%-35%. (In addition, the same studies discovered that catecholamine turnover is also higher from training. Thyroxine has demonstrated an increase in total adrenaline in the adrenal glands of rats.)

Exercise training caused changes in thyroid levels of male athletes, highly trained.

Another study shows that physical training stimulates the metabolism of thyroid hormones; increases thyroid use and turnover.

Conflicting studies on exercise
To be fair, study with mostly inconclusive results about thyroid levels in response to exercise,
T3, T4 levels were not affected by a bout of exercise, but growth hormone increased.

Thyroid respect to Diet
Plasma concentrations of T3 and T4 increased in response to high-fat, high-sugar, or high-calorie meals, possibly suggesting that a meal can induce the secretion of T4 or T3.
Thyroid hormone is associated with ketosis, where thyroid hormone availability is associated with lipolysis and ketogenesis.
Abstract goes on to inform us that norepinephrine increases ketogenesis by stimulating lipolysis. Nicotine stimulates the release of norepinephrine. Caffeine can also raise norepinephrine levels.

When % dietary fat was increased from 30% to 50% in this study, the formerly obese women showed a reduced T3/T4 ratio after a dinner meal.


Thyroid fluctuation with circadian rhythm:
Thyroid levels really can fluctuate in animals,
thyroid fluctuation evidence++,
in STARVED animals,
Thyroid axis and melatonin in humans,
Ketogenic Diet Disrupts the Circadian Clock

Composition of diet (low-fat/high-fat) altered the circadian rhythms in levels triiodothyronine (T3). In the high-fat diet. After 24 hrs of fasting, insulin and glucose were found to vary with time of day. However, in the high-fat diet oscillations in T3 were not detected, but for the low-fat diet they were.

More evidence of thyroid osciallations with respect to circadian rhythm. Interestingly, the oscillations were affected by fasting at 24 hr intervals, but not at 48 hr intervals. The point is that osciallations in thyroxine (T4), insulin, and glucose were affected by the time of day. The abstract mentions a "dependence of the stimulus on the time of day", and doesn't really explain much on what this stimulus is, but I assume they meant the stimulus of having a meal.

Regulation of UCP2
UCP2 is a mitochondrial protein, and studies continue to reveal its role in various tissues of the body.
In a study (yr 2000) on human subjects, UCP2 expression was markedly upregulated in the adipose tissue of subjects with higher thyroid activity.