Effect of iron-deficiency anemia on hormone levels and thermoregulation during cold exposure

Abstract

When exposed to an ambient temperature of 4 degrees C, iron-deficient anemic rats become hypothermic. This lesion is related more to anemia than to tissue iron deficiency, since exchange transfusion to hematocrits over 25 restored normal thermoregulatory performance. Likewise poor cold responses were induced in control rats by transfusion to low hematocrits. Cold sensitivity in all anemic animals was paralleled by poor thyroid responses: there was a significant positive correlation between hematocrit and percent rise in triiodothyronine (r = 0.63) and thyroxine (r = 0.53) during 6 h at 4 degrees C. Basal levels of thyroid-stimulating hormone (TSH) were similar in control and iron-deficient animals: after cold exposure, TSH rose to higher levels in those animals with hematocrits over 25 than in those with lower hematocrits. Diminished O2 delivery to tissues responsible for heat production is probably a major component of the cold sensitivity of anemic rats. The novel finding that thyroid hormone responses are compromised by anemia implies effects on hormonal regulation that may also contribute to this functional lesion.

Effects of administration of iron, iodine and simultaneous iron-plus-iodine on the thyroid hormone profile in iron-deficient adolescent Iranian girls

“…The present study explored the hypothesis that iron deficiency might impair thyroid metabolism, as previously reported in animal and human studies (Dallman et al, 1978, 1980; Chen et al, 1983;Beard et al, 1984Beard et al, , 1990aMartinez-Torres et al, 1984;Brigham and Beard, 1995). Our findings confirm that an improvement in iron status had a positive impact on serum concentrations of thyroid hormones in iron-deficient adolescent girls.…”

“…Theoretically, severe iron deficiency could lower thyroperoxidase activity and interfere with thyroid hormone synthesis. Animal studies have documented that weanling rats fed iron-deficient diets have significantly lower T3 and T4 compared to rats fed adequate iron (Chen et al, 1983;Beard et al, 1984;Brigham and Beard, 1995). Recently Hess and co-workers (2002) showed that thyroid peroxidase activity is significantly reduced in iron deficiency anaemia.…”

“…Studies in animals and humans have shown that iron deficiency with or without anaemia impairs thyroid hormone metabolism. Nutritional iron deficiency has been shown to significantly lower the circulating levels of both thyroxine and triiodothyronine in rats (Chen et al, 1983;Beard et al, 1984;Brigham and Beard, 1995), and to reduce conversion of T4-T3 (Dillman et al, 1980). Iron deficiency also impairs thyroid metabolism in human studies.…”

The effects of iron deficiency anemia on the thyroid functions

“…The studies carried out in rats have indicated that iron, T4 and T3 levels in circulation were significantly decreased during conversion of thyroxine (T4) to triiyodotironin (T3). [4][5][6][7] However, effects of iron deficiency anemia on thyroid function-related studies are mostly based on animal studies and results are contradictory.…”

Postnatal iron status of Hong Kong Chinese women in a longitudinal study of maternal nutrition

“…These include impaired work performance (Cook et al, 1994;Lozoff et al, 1998), behaviour and intellectual performance (Moffatt et al, 1994). In addition, impaired thermoregulatory mechanisms (Beard et al, 1984) and an increased risk of infection (Dallman, 1987) have been documented in iron de®ciency status. Iron de®ciency has also been found to be associated with adverse pregnancy outcomes (Yip & Dallman, 1996).…”