However, Saturday saw me once again push the limits of my endurance along with 200 other competitors. It must be said that none of us were doing this for health or fitness, most were taking part for the challenge, to be involved in a unique event on its 100th year, and for some the ultimate glory of winning.
The above photo is my temperature post event, a reading which continued for 3 days. For those that aren't familiar with temperature readings in relation to health, simply put, it isn't a good state to be in.
"Hypothermia happens when a person's body temperature drops below 35°C (95°F). Normal body temperature is around 37°C (98.6°F)." - National Health Service (NHS)
Whilst I wasn't hospitalised by it, nor would I consider it hypothermia, I displayed a host of symptoms of the after effects of engaging in endurance exercise.
“I’m not sure who introduced the term “aerobic” to describe the state of anaerobic metabolism that develops during stressful exercise, but it has had many harmful repercussions. In experiments, T3 production is stopped very quickly by even “sub-aerobic” exercise, probably because of the combination of a decrease of blood glucose and an increase in free fatty acids. In a healthy person, rest will tend to restore the normal level of T3, but there is evidence that even very good athletes remain in a hypothyroid state even at rest. A chronic increase of lactic acid and cortisol indicates that something is wrong. The “slender muscles” of endurance runners are signs of a catabolic state, that has been demonstrated even in the heart muscle. A slow heart beat very strongly suggests hypothyroidism. Hypothyroid people, who are likely to produce lactic acid even at rest, are especially susceptible to the harmful effects of “aerobic” exercise. The good effect some people feel from exercise is probably the result of raising the body temperature; a warm bath will do the same for people with low body temperature.” - Ray Peat
Participents in the Baylor & Hackney (1) study undertook a program of weight lifting, rowing and running. T3 levels decreased initially but returned to baseline levels by the end of the study. The Boyden, Pamenter, Rotkis, Stanforth, Wilmore, (2) study involved a group of women running on average of 14 miles per week, who then increased to 44 miles and subsequently 64 miles. This saw initial an initial decrease in thyroid function but overtime function was restored.
T3 acts in various ways to increase heat production. (3) With normal T3 levels you have adequate energy maintain metabolic function including heat production, not enough and the body will surpass heat production to regulate precious energy. This isn't a bad thing, it is just physiology, a metabolic adaption in order to maintain life. Survival is the name of the game and if you engage in endurance exercise whilst being in a calorie deficit (remember I tried to consume as many calories as I could but it is simply too hard to get the necessary amount over that period of time), then it's no wonder the thyroid slows to counter the environment it is facing. Due to this excessive energy expenditure (8 hours) my body compensated in order to ensure my survival. The decrease of T3 production increased my efficiency and slowed the rate at which I used my energy.
I'm not suggesting that endurance exercise has negative effects for all, no doubt in conditioned athletes they are able to survive for longer, but metabolic adaptions seem necessary and the degree of adaption will no doubt depend upon circumstances. Extreme endurance must down-regulate your thyroid, it has to in order for you to survive the event and it isn't wrong that this adaption occurs, if your a professional supported athlete you may be able to limit this adaption. The problem occurs when extreme exercise is prolonged (and often viewed as healthy) without adequate time to rest and repair, which is often is also coupled with caloric restriction (either intentionally or by those unaware of their need for increased intake).
Brown, argues that disagnosing hypothyroidism in endurance athletes is "consistent with research showing that extreme stress is often a trigger for the condition." Mainstream medicine uses the thyroid Stimulating Hormone (TSH) test as the standard for diagnosis and those who fall within the "normal" reference range of 0.4 to 4.5 receive no help despite possibly displaying other symptoms such as decreased body temperature.
"According to American College of Endocrinology literature, the range of normal TSH level is broad, from 0.5 to an upper limit of near 5, depending on a patient’s gender, age and other factors. In practice, many endocrinologists consider TSH levels above 4—combined with symptoms such as fatigue—evidence of an underactive thyroid. Brown and a small camp of other endocrinologists argue that thyroid insufficiency can be signalled by a TSH level as low as 2, for which Brown cites some recently published research. By their standards, about 10% of the population is hypothyroid—double the 5% that is cited by mainstream endocrinology. Jeffrey Garber, American College of Endocrinology president, said hypothyroidism increasingly is being diagnosed in people who don’t have it, by endocrinologists whom Garber labeled as “alternative.” “The alternative crowd is saying, ‘Gee, this is why you’re not feeling better, because these [mainstream] doctors are clueless,’ ” Garber said. So if this reporting is accurate, Brown is looking at the same test results and seeing what he believes to be thyroid disease, where his peers see normal thyroid function."
"In the 1930′s accurate diagnosis was made by evaluating a variety of indications, including basal oxygen consumption, serum cholesterol level, pulse rate, temperature, carotenemia, bowel function, and quality of hair and skin. A good estimate can be made using only the temperature and pulse rate. - Ray Peat
"Delayed relaxation of deep tendon reflexes (Woltman sign)1 is seen in about 75% of patients with hypothyroidism and has a positive predictive value of 92% in overtly hypothyroid patients.2 In unaffected patients, the relaxation time for deep tendon reflexes is 240–320 ms. Delays in relaxation time in patients with hypothyroidism appears to be proportional to the level of thyroid-hormone deficiency. As sensitive blood assays become more widely available around the world, the Woltman sign is likely to become obsolete as a diagnostic tool."
“One of the oldest tests for hypothyroidism was the Achilles tendon reflex test in which the rate of relaxation of the calf muscle corresponds to thyroid function–the relaxation is slow in hypothyroid people. Water, sodium, and calcium are more slowly expelled by the hypothyroid muscle. Exactly the same slow relaxation occurs in the hypothyroid heart muscle, contributing to heart failure, because the semi-contracted heart can’t receive as much blood as the normally relaxed heart. The hypothyroid blood vessels are unable to relax properly, contributing to hypertension. Hypothyroid nerves don’t easily return to their energized relaxed state, leading to insomnia, parasthesias, movement disorders, and nerves that are swollen and very susceptible to pressure damage.” - Ray Peat
Baylor, L,S., and Hackney, A,C. (2003). Resting thyroid and leptin hormone changes in women following intense, prolonged exercise training. Eur. J Appl. Physiol. Jan;88(4-5):480-4.
Boyden T,W., and Pamenter, R.W., Rotkis, T,C., Stanforth, P., and Wilmore, J,H. (1984). Thyroidal changes associated with endurance training in women. Med. Sci. Sports Exerc. Jun;16(3):243-6.
Goglia, F., Moreno, M., and Lanni, A. (1999). Action of thyroid hormones at the cellular level: the mitochondrial target. FEBS Lett. Jun 11;452(3):115-20.