The Thyroid Function in Young Men During Prolonged Exercise and the Effect of Energy and Sleep Deprivation

Abstract

Thyroid function has been investigated in 24 young military cadets participating in a 5 d ranger training course with heavy physical exercise, calorie deficiency and deprivation of sleep. The cadets were divided into three groups, each differing in the amount of sleep and food consumption. The serum levels of thyroid hormones (T4, FT4, T3, rT3) and TBG showed a biphasic pattern during the course. Initially there was an increased secretion concomitant with an increased deiodination of T4 to T3 and rT3 mainly due to physical exercise. When the activities lasted for several days without sufficient food supply the thyroid secretion decreased simultaneously with an alteration of the peripheral conversion of T4 to rT3 instead of T3. A significant correlation was found between the changes in total and free thyroxine (r = 0.9) and between the increase in rT3 and decrease in T3 (r = 0.6). TSH decreased during the first day of activities and remained low throughout the course. The TSH response to TRH stimulation was greatly reduced during the course due to physical exercise and calorie deficiency. The present investigation demonstrates that the thyroid function is strongly affected by prolonged physical exercise and a negative energy balance, whereas sleep deprivation does not have any significant influence. The results indicate that the alteration observed is not regulated just by the hypothalamo-pituitary-thyroid-axis alone.

The effects of maximal aerobic exercise on cortisol and thyroid hormones in male field hockey players

“…Physical exercise has been reported to stimulate the peripheral deiodination of T4 and an increased uptake of T4 in the liver during exercise (Opstad et al, 1984). Increased conversion of T4 to T3 by peripheral tissues during training is improbable since there were no significant changes in serum fT3 concentrations after immediately exercise in the present study.…”

Field studies of exercise and food deprivation

“…Prolonged exercise alone does not appear to produce this effect [28]. This reduction in fast-twitch muscle fibers is probably a consequence of a decline in activity in the thyroid axis [29], as has been noted in field studies of prolonged work with inadequate dietary intakes [8,30]. Similar findings are evident in obese patients on a very low calorie diet [31].…”

Hormonal Responses to Exercise and Training: A Short Review

“…Most workers find no change in plasma TSH during acute exercise (Terjung & Tipton, 1971;Mason et al, 1973;Dessypris et al, 1977Dessypris et al, , 1980Stock et al, 1978;Gawel et al, 1979) although a slight fall has also been reported (Grossman et al, 1984;Opstad et al, 1984). One study suggested an anticipatory rise in TSH in untrained subjects (Mason et al, 1973) and another a rise in TSH after, but not during, prolonged exertion (Refsum & Stromme, 1979).…”

“…Most studies agree that intensive acute exercise causes a rise in plasma T4, free T4 index, free T4 and T3 (Terjung & Tipton, 1971;Kirkeby et al, 1977;Stock et al, 1978;O'Connell et al, 1979;Refsum & Stromme, 1979;Opstad et al, 1984) although no change was reported during a marathon run in one study (Dessypris et al, 1980) and isolated studies have reported a fall of either T4 (DeNayer et al, 1968) or T3 (O'Connell et al, 1979). Most workers find no change in plasma TSH during acute exercise (Terjung & Tipton, 1971;Mason et al, 1973;Dessypris et al, 1977Dessypris et al, , 1980Stock et al, 1978;Gawel et al, 1979) although a slight fall has also been reported (Grossman et al, 1984;Opstad et al, 1984).…”

“…The luteal progesterone rise is abolished in amenorrhoeic subjects but is often also diminished in athletes who continue to menstruate (Shangold et a/., 1979;Bonen et al, 1981;Bullen et al, 1985). This 'inadequate luteal phase' is the first abnormality to appear when women are subjected to an intensive exercise programme (Bullen et al, 1985) and may represent an important clinical problem as a hidden cause of infertility (Prior et al, 1982).…”