Seasonal variations of total and free thyroid hormones in healthy men: a chronobiological study

Pasquali, Renato; Baraldi, Giovanna; Casimirri, Francesco; Mattioli, Loretta; Capelli, M.; Melchionda, Nazario; Capani, F; Labò, G

doi:10.1530/acta.0.1070042

Cited by 19 publications

(13 citation statements)

References 8 publications

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“…This finding agrees with some previous reports (Halberg et al 1983;Konno et al 1982), but not with all of them (Pasquali et al 1984;Rastogi et al 1976). A significant inverse relationship between basal TSH levels and the ambient temperature has been found (Konno et al 1982), and it may partly explain the increased secretion of TSH in spring in our study, because the average temperature in October is higher than in March.…”

Section: Discussionsupporting

confidence: 91%

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Serum concentrations of thyrotropin, thyroxine, triiodothyronine and thyroxine binding globulin in female endurance runners and joggers

Hohtari

Pakarinen

Kauppila

1987

Acta Endocrinologica

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The effects of endurance training and season on the function of the anterior pituitary-thyroid axis were studied in 18 female runners and their 12 controls, and in 13 joggers and their 11 controls in Northern Finland, with a large seasonal difference in environmental factors. The serum concentrations of thyrotropin (TSH), thyroxine (T4), free thyroxine (fT4), triiodothyronine (T3), thyroxine binding globulin (TBG) and oestradiol (E2) were measured during one menstrual cycle in the light training season (autumn) and in the hard training season (spring). The responses of TSH to intravenous TRH stimulation were also measured in the luteal phase of the cycle during the hard training season. Endurance running did not affect the basal or TRH-stimulated serum TSH concentrations, while those of T4 and fT4 in runners were lowered in both seasons and that of T3 in the light training season in relation to control subjects. The serum concentrations of TBG were also significantly lower in runners than their controls in the luteal phase in both seasons. The effect of jogging on thyroid hormones was less pronounced. Serum concentrations of TSH, T4, fT4, T3 and TBG were generally slightly higher in spring than in autumn. Strenuous endurance training seems to have minor changes on the function of the thyroid gland. Depressed T4 levels in runners may rather be due to lowered TBG levels than due to direct effect of training. In spring the function of anterior pituitary-thyroid axis is more active than in autumn.The hypothalamic-pituitary-thyroid axis is sensi¬ tive to stress. During pregnancy the function of the thyroid gland increases (Burrow 1975), while in non-thyroidal illnesses, including infections, renal and hepatic diseases and starvation, the serum concentration of triiodothyronine (T3) de¬ creases and that of serum thyroxine (T4) show minor alterations (Schimmel et al. 1977).Endurance training is a hard physical stress which decreases the amount of body fat and increases demands on the energy supply, and which is partly regulated by thyroid hormones. Secretion of thyrotropin (TSH) is also under the stimulatory control of oestrogens (Labrie et al.1978), the concentrations of which, however, are decreased in female runners (Boyden et al. 1983;Ronkainen et al. 1985). Physical exercise may thus affect the function of the anterior pituitary-thy¬ roid axis of women by different mechanisms. The effects of such training on the pituitary-thyroid axis have been evaluated only in few investiga¬ tions, dealing with ballet dancers (Warren 1980) and runners (Boyden et al. 1982(Boyden et al. , 1984Marcus et al. 1985). The results in these studies have been conflicting; decreased, unchanged or increased responses of TSH and thyroid hormones to stre¬ nuous exercise have been reported.To gain information on the association of the function of the pituitary-thyroid axis and chronic, intense training in women, we measured serum concentrations of TSH, thyroid hormones, thyro¬ xine binding globulin (TBG) and oestradiol (E2) of runners, jogge...

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Section: Discussionsupporting

confidence: 91%

“…In other studies a seasonal variation of TBG has been absent (Rastogi et al 1976), or its level has been high in autumn and low in March-July (Pasquali et al 1984). The reason for the increased TBG level in spring in our study is unclear.…”

Section: Discussioncontrasting

confidence: 58%

Serum concentrations of thyrotropin, thyroxine, triiodothyronine and thyroxine binding globulin in female endurance runners and joggers

Hohtari

Pakarinen

Kauppila

1987

Acta Endocrinologica

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“…*The best fitting model. (3,4,7,9,17,27). The absence of a phenotypic correlation between serum TSH and the thyroid hormone levels in a healthy population attracts particular attention.…”

Section: Discussionmentioning

confidence: 99%

Genetic and environmental interrelations between measurements of thyroid function in a healthy Danish twin population

Hansen¹,

Brix²,

Iachine³

et al. 2007

American Journal of Physiology-Endocrinology and Metabolism

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Hansen PS, Brix TH, Iachine I, Sørensen TI, Kyvik KO, Hegedüs L. Genetic and environmental interrelations between measurements of thyroid function in a healthy Danish twin population. Am J Physiol Endocrinol Metab 292: E765-E770, 2007. First published November 7, 2006 doi:10.1152/ajpendo.00321.2006, free thyroxine (T4), and free triiodothyronine (T3) levels illustrate the thyroid function set point, but the interrelations between these have never been characterized in detail. The aim of this study was to examine the associations between TSH and thyroid hormone levels in healthy euthyroid twins and to determine the extent to which the same genes influence more than one of these biochemical traits; 1,380 healthy euthyroid Danish twins (284 monozygotic, 286 dizygotic, 120 opposite-sex twin pairs) were recruited. Genetic and environmental associations between thyroid function measurements were examined using quantitative genetic modeling. In bivariate genetic models, the phenotypic relation between two measurements was divided into genetic and environmental correlations. Free T4 and free T3 levels were positively correlated (r ϭ 0.32, P Ͻ 0.0001). The genetic correlation between serum free T4 and free T3 levels was rg ϭ 0.25 (95% CI 0.14 -0.35), suggesting that a set of common genes affect both phenotypes (pleiotropy). The correlation between the environmental effects was re ϭ 0.41 (0.32-0.50). From this we calculated that the proportion of the correlation between free T 4 and free T 3 levels mediated by common genetic factors was 48%. Only 7% of the genetic component of serum free T 3 levels is shared with serum free T 4. Serum TSH and thyroid hormone levels did not share any genetic influences. In conclusion, thyroid hormone levels are partly genetically correlated genes that affect free T 4 levels and exert pleiotropic effects on free T 3 levels, although most of the genetic variance for these measurements is trait specific.thyroid-stimulating hormone; thyroid hormones; twin study; bivariate analyses THE SERUM THYROTROPIN (TSH), free thyroxine (T 4 ), and free triiodothyronine (T 3 ) levels represent measurements of the thyroid function set point, reflected from different angles. Twin and family studies have shown that genetic factors exert considerable influence on the levels of each of these biochemical measurements (6,12,14,20). We (6) have previously demonstrated that ϳ0.65 of the variation in serum TSH level was explained by genetic influences. Almost identical heritability estimates were found for serum free T 4 (0.65) and free T 3 (0.64) levels (6). In other studies, the heritability estimates range from 0.32 to 0.67, lowest for serum TSH levels and highest for serum T 3 (12,14,20). Many genes are involved in the regulation of these measurements, and several polymorphisms located in thyroid hormone pathway genes, such as the TSH receptor gene as well as the deiodinase genes, have been shown to be associated with TSH levels as well as thyroid hormone levels (18,19).It seems plausible that serum TSH, free T ...

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“…In hypothyroid subjects, lower serum T 4 levels and higher serum TSH levels and TSH responses to TRH were found in winter rather than in summer (Konno & Morikawa 1982). In another study, involving large populations, the serum TSH levels of young, middle-aged and old Italian subjects were at their highest in December in the middleand old-age classes (Simoni et al 1990), but no seasonal changes were seen in younger subjects (Pasquali et al 1984, Simoni et al 1990). In a recent study both serum TSH and free T 3 were highest in winter in healthy Belgian subjects (Maes et al 1997).…”

Section: Introductionmentioning

confidence: 89%

The pituitary-thyroid axis in healthy men living under subarctic climatological conditions

Hassi

Sikkilä²,

Ruokonen³

et al. 2001

Journal of Endocrinology

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In order to evaluate the effects of climatic factors on the secretion of thyroid hormones and TSH in a high latitude population, we have taken serum and urine samples from 20 healthy men from northern Finland (67 -68 N) every 2 months for a period of 14 months. Serum free triiodothyronine (T 3 ) levels were lower in February than in August (3·9 vs 4·4 pmol/l, P<0·05) and TSH levels were higher in December than during other months (2·1 vs 1·5-1·7 mU/l, P<0·01). Serum total and free thyroxine (T 4 ), total T 3 and reverse T 3 levels and urinary T 4 levels were unchanged. Urinary T 3 levels were significantly higher in winter than in summer. Serum free T 3 correlated highly significantly with the outdoor temperature integrated backwards weekly for 7-56 days (r=0·26 for 1-56 days) from the day when the blood samples were taken. Serum TSH did not show any significant correlation with the thyroid hormones or with the integrated temperature of the previous days, but it did show an inverse and significant correlation (r= 0·31) with the ambient luminosity integrated backwards for 7 days from the day when the blood sample was taken. The gradually increasing correlation between outdoor temperatures and serum free T 3 suggests that the disposal of thyroid hormones is accelerated in winter, leading to low serum free T 3 levels and a high urinary free T 3 excretion. Since there was no correlation between thyroid hormones and serum TSH, the feedback mechanism between TSH and thyroid hormones may not be the only contributing factor, and other factors such as ambient luminosity may at least partly determine serum TSH in these conditions. Also urinary free T 3 appears to be a novel and non-invasive indicator for thyroid physiology.

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Seasonal variations of total and free thyroid hormones in healthy men: a chronobiological study

Cited by 19 publications

References 8 publications

Serum concentrations of thyrotropin, thyroxine, triiodothyronine and thyroxine binding globulin in female endurance runners and joggers

Serum concentrations of thyrotropin, thyroxine, triiodothyronine and thyroxine binding globulin in female endurance runners and joggers

Genetic and environmental interrelations between measurements of thyroid function in a healthy Danish twin population

The pituitary-thyroid axis in healthy men living under subarctic climatological conditions

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