Thyroid status of humans at high altitude

Chakraborty, Sudipto; Samaddar, Julia S.; Batabyal, Subhasis

doi:10.1016/0009-8981(87)90205-1

Cited by 11 publications

(9 citation statements)

References 2 publications

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“…Our findings of unaltered baseline TSH concentration, but elevated levels of both total and free fractions of T3 and T4 are consistent with most of the previous studies (8,12,22,30,31,39,43), suggesting that a slight hyperthyroidism may be necessary to withstand the extreme environments of high altitude (4). Thyroid hormones increase the levels of 2,3-diphosphoglyceric acid in erythrocytes, facilitating oxygen release to the tissues, by causing a shift of the oxyhemoglobin dissociation curve to the right, advantageous in hypoxia (42).…”

Section: Discussionsupporting

confidence: 95%

“…The T4 degradation rate increases during the first 3 days at altitude and thereafter remains slightly elevated, thus contradicting decreased clearance as a possible cause of T4 elevation (46). In men trekking at altitudes around 3,500 m, thyroxine-binding globulin (TBG) levels were found sufficiently elevated to explain a concomitant T4 rise (8). However, in most studies, small or no changes in TBG and thyroxine-binding prealbumin have been found (26,31,39,45).…”

Section: Discussionmentioning

confidence: 95%

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Effects of high-altitude hypoxia on the hormonal response to hypothalamic factors

Richalet

Letournel

Souberbielle

2010

American Journal of Physiology-Regulatory, Integrative and Comp

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Acute and chronic exposure to high altitude induces various physiological changes, including activation or inhibition of various hormonal systems. In response to activation processes, a desensitization of several pathways has been described, especially in the adrenergic system. In the present study, we aimed to assess whether the hypophyseal hormones are also subjected to a hypoxia-induced decrease in their response to hypothalamic factors. Basal levels of hormones and the responses of TSH, thyroid hormones, prolactin, sex hormones, and growth hormone to the injection of TRH, gonadotropin-releasing hormone, and growth hormone-releasing hormone (GHRH) were studied in eight men in normoxia and on prolonged exposure (3-4 days) to an altitude of 4,350 m. Thyroid hormones were elevated at altitude (+16 to +21%), while TSH levels were unchanged, and follicle-stimulating hormone and prolactin decreased, while leutinizing hormone was unchanged. Norepinephrine and cortisol levels were elevated, while no change was observed in levels of epinephrine, dopamine, growth hormone (GH), IGF-1, and IGFBP-3. The mean response to hypothalamic factors was similar in both altitudes for all studied hormones, although total T4 was lower in hypoxia during 45 to 60 min after injection. The effect of hypoxia on the hypophyseal response to hypothalamic factors was similar among subjects, except for the GH response to GHRH administration. We conclude that prolonged exposure to high-altitude hypoxia induces contrasted changes in hormonal levels, but the hypophyseal response to hypothalamic factors does not appear to be blunted.

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Section: Discussionsupporting

confidence: 95%

Section: Discussionmentioning

confidence: 95%

Effects of high-altitude hypoxia on the hormonal response to hypothalamic factors

Richalet

Letournel

Souberbielle

2010

American Journal of Physiology-Regulatory, Integrative and Comp

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“…This rise in total thyroid hormones at high altitude (HA) has been confirmed by several other investigators (Stock et al 1978;Wright 1979;Mordes et al 1983;Chakraborty et al 1987) and appears to be independent of increased pituitary drive since the basal thyrotropin (TSH) and its response to TSH releasing hormone (TRH) remain unaltered (Rastogi et al 1977). In addition, the rise in hormone levels was also evident when pituitary secretion of TSH was suppressed by T4 administration (Sawhney and Malhotra 1991).…”

Section: Introductionmentioning

confidence: 60%

Free and total thyroid hormones in humans at extreme altitude

et al. 1995

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Alterations in circulatory levels of total T4 (TT4), total T3 (TT3), free T4 (FT4), free T3 (FT3), thyrotropin (TSH) and T3 uptake (T3U) were studied in male and female sea-level residents (SLR) at sea level, in Armed forces personnel staying at high altitude (3750 m) for prolonged duration (acclimatized low-landers, ALL) and in high-altitude natives (HAN). Identical studies were also performed on male ALL who trekked to an extreme altitude of 5080 m and stayed at an altitude of more than 6300 m for about 6 months. The total as well as free thyroid hormones were found to be significantly higher in ALL and HAN as compared to SLR values. Both male as well as female HAN had higher levels of thyroid hormones. The rise in hormone levels in different ALL ethnic groups drawn from amongst the southern and northern parts of the country was more or less identical. In both HAN and ALL a decline in FT3 and FT4 occurred when these subjects trekked at subzero temperatures to extreme altitude of 5080 m but the levels were found to be higher in ALL who stayed at 6300 m for a prolonged duration. Plasma TSH did not show any appreciable change at lower altitudes but was found to be decreased at extreme altitude. The increase in thyroid hormones at high altitude was not due to an increase in hormone binding proteins, since T3U was found to be higher at high altitudes.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…1987;Sawhney and Malhotra 1991). Surks (1966b) believed that the plasma dehydration during the initial period of altitude exposure is probably responsible for the alteration in the concentration of circulating thyroid hormones, while other authors have been of the opinion that the transient increase in circulating thyroid hormones in hypoxic subjects may be attributed to a shift of particular hormones from the extravascular to the intravascular compartment (Kotchen et al 1973) without any pituitary-mediated change in overall thyroid status (Kotchen et al 1973;Chakraborthy et al 1987). The present study was not designed to examine the involvement of the pituitary in the alteration of thyroid function in subjects exposed to hypobaric hypoxia.…”

Section: Discussionmentioning

confidence: 97%

“…Altered levels of circulating thyroid hormones in sojourners returned to their pre-exposure values after their return to sea level (Surks 1966b;Kotchen et al 1973;Rastogi et aI. 1977;Wright 1979;Chakraborthy et al 1987;Sawhney and Malhotra 1991). Some authors believe that the absence of an increase in TSH concentration and the rapid alteration in the levels of thyroxine probably indicate a shift of hormones from the extravascular to the intravascular compartment at altitude, rather than enhanced pituitary-mediated thyroxine secretion.…”

Section: Introductionmentioning

confidence: 91%

Thyroidal handling of radioiodine in sea level residents exposed to hypobaric hypoxia

et al. 1993

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In the present investigation thyroidal accumulation of radioiodine and its release were assessed by direct testing of thyroid function using radioactive iodine, in vivo, in sea level residents intermittently exposed to hypobaric hypoxia. Thyroidal accumulation of radioiodine and its turnover were examined daily for 14 days. Twelve healthy human male volunteers were divided into three groups, with an equal number of individuals in each group. A decompression chamber was used to expose each group of subjects to hypoxic conditions at a simulated altitude of 3810 m for 8 h/day for 14 days. An oral dose of 25 mu Ci iodine-131 was administered to each individual of the first group immediately before the initiation of intermittent hypoxia. The second group of subjects received a tracer dose at the beginning of the 4th day of the 14 days, intermittent exposure to hypoxia, while the third group received the tracer dose 1 week after the completion of the exposure. Control studies were carried out on the subjects before they were subjected to the experimental conditions. Thyroidal accumulation of 131I in experimental subjects during the hypoxic state and in the post-hypoxic state was higher than in the control studies. The pattern of accumulation during exposure to hypoxia and in the post-hypoxic state showed multiple peaks of radioactive iodine uptake (PRAIU), a unique feature. The multiple PRAIU by the thyroid in experimental subjects were sharp and of short duration, reflecting an increased rate of 13I release from the thyroid. Control subjects had a single PRAIU by the thyroid 24 h after the administration of tracer.

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Thyroid status of humans at high altitude

Cited by 11 publications

References 2 publications

Effects of high-altitude hypoxia on the hormonal response to hypothalamic factors

Effects of high-altitude hypoxia on the hormonal response to hypothalamic factors

Free and total thyroid hormones in humans at extreme altitude

Thyroidal handling of radioiodine in sea level residents exposed to hypobaric hypoxia

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