found this verty intersting to mallet's thermoregulation protocol

[hardasnails1973]

IRON DEFICIENCY AND THERMOREGULATION
The following studies offer evidence that the inability to maintain body temperature (feeling cold when others are warm) is due to iron deficiency. Most hypos experience this, indicating that iron deficiency is usually a factor in hypothyroidism.



IRON DEFICIENCY AND SUPPLEMENTATION IMPACT THERMOREGULATION AND BROWN ADIPOSE TISSUE (BAT) MITOCHONDRIAL MORPHOLOGY OF RATS EXPOSED TO COLD

Author(s):

MICHELSEN KIM G HALL CLINTON B NEWMAN JR SAMUEL M DROKE ELIZABETH A SLEEPER MARY E LUKASKI HENRY C

Interpretive Summary:

The role that iron (Fe) plays in regulating whole-body temperature is not well defined. Fe-deficient rats have reduced concentrations of thyroid hormones and altered body temperature. Because thyroid hormones act at the mitochondria level of brown adipose tissue to produce heat, Fe status may affect the structural characteristics of mitochondria, a cell component that produces energy to maintain body temperature. To examine the relationships among dietary iron, body temperature, thyroid hormones, and brown adipose tissue mitochondria, young male rats were fed diets containing adequate or deficient amounts of Fe. Some of the rats fed the low-Fe diets then were given the diet containing an adequate amount of Fe. When exposed to cold air for four hours, the rats fed the Fe-deficient diet had a greater decline in body temperature than the rats fed the Fe- adequate diet. The rats initially fed the Fe-deficient diet then fed the Fe-adequate diet had similar body temperatures as the animals fed the Fe- adequate diet. Plasma thyroid hormone concentrations were less in the rats fed the Fe-deficient, as compared to the Fe-adequate and Fe-deficient supplemented with adequate Fe diets. The structure of mitochondria suggests that Fe deficiency produced changes that indicate impaired heat production; this change was ameliorated with Fe supplementation. These findings indicate that Fe deficiency reduces the capability of rats to maintain body temperature during short-term cold exposure. Biological impairments of Fe deficiency lie in the production of adequate amounts of thyroid hormones and adverse changes in the mitochondria that inhibit the production of heat. This information will be useful to scientists who seek to understand how mineral elements regulate energy utilization.

[hardasnails1973]

IRON DEFICIENCY

Several key observations have stimulated interest in the relationship
between iron deficiency and thermoregulation. Iron-deficient anemic rats
were found to be unable to maintain normal body temperature when exposed to
cold (39°F [4°C]) (Beard et al., 1982, 1984; Dillmann et al., 1979, 1980).
Accompanying the impairment in thermoregulation were a decrease in the rate
of thyroid hormone turnover and an increase in the rate of norepinephrine
turnover, as compared to those observed in noniron-depleted cold-exposed
(control) rats. Iron-deficient humans are unable to maintain their body
temperature during exposure to cool water (82°F [28°C]) (Beard et al.,
1990a; Martinez-Torres et al., 1984) or cool air (61°F [16°C]) (Lukaski et
al., 1990), compared to subjects with normal iron status and equivalent body
composition. Additionally, the iron-deficient subjects had lower thyroid
hormone (Beard et al., 1990a) and higher catecholamine responses to cold
(Lukaski et al., 1990; Martinez-Torres et al., 1984), similar to the
response of iron-deficient rats. After repletion with iron supplements, the
previously iron-deficient human subjects showed improved ability to maintain
body temperature in the cold. These observations clearly demonstrate the
link between iron deficiency and poor thermoregulation.

Anemia vs. Tissue Iron Deficiency

Iron deficiency may exert its effects on thermoregulation through two
distinct, yet related, mechanisms, one involving anemia and the other
involving tissue iron deficiency. Iron-deficiency anemia results in
decreased oxygen transport from the lungs to tissues, and this reduction in
oxygen availability inhibits physiological responses to cold, including
peripheral vasoconstriction, a heat-conserving process, and increased
metabolic rate, a heat-generating process. Hypoxia, created by reducing the
oxygen content or the pressure of inspired air, results in hypothermia in
rodents (Gautier et al., 1991). The inability to conserve and produce body
heat properly accounts for hypoxia-induced hypothermia (Wood, 1991). Lack of
oxygen availability for aerobic metabolism causes a decrease in metabolic
rate and, subsequently, a decrease in heat production. Hypoxic rats
demonstrate decreased shivering and nonshivering thermogenesis (Gautier et
al., 1991) and a decrease in body temperature set-point (Gordon and
Fogelson, 1991). Impaired neural control of these processes may also account
for the effects of hypoxia on thermoregulation (Mayfield et al., 1987).
Tissue iron deficiency, apart from anemia, decreases the ability of muscles
to utilize energy for muscular contraction, presumably via a decrease in the
activity of mitochondrial iron-containing enzymes required for the oxidative
production of ATP (Davies et al., 1984).