Human cold air habituation is independent of thyroxine and thyrotropin

1992 ◽  
Vol 72 (6) ◽  
pp. 2134-2139 ◽  
Author(s):  
R. L. Hesslink ◽  
M. M. D'Alesandro ◽  
D. W. Armstrong ◽  
H. L. Reed
Keyword(s):  
Single Daily Dose ◽  
Plasma Norepinephrine ◽  
Free T4 ◽  
Cold Air ◽  
Brown Adipose ◽  
Daily Dose ◽  
Before And After ◽  
Serum T4 ◽  
The Relationship ◽  
Serum Tsh

Thyroxine (T4) is required in species possessing brown adipose tissue (BAT) for the maintenance of cold tolerance and adaptation. In humans, who possess negligible quantities of BAT, the importance of T4 has not been demonstrated. We studied the effects of decreased serum T4 and thyrotropin (TSH) on human cold habituation after repeated cold air exposures. Eight men (T3+) received a single daily dose of triiodothyronine (T3; 30 micrograms/day), and another eight men (T3-) received a placebo. All 16 normal thyroid men underwent a standardized cold air test (SCAT) under basal conditions in January and again in March after eighty 30-min 4.4 degrees C air exposures (10/wk). Measurements of basal metabolic rate (BMR), O2 consumption (VO2), mean arterial pressure (MAP), plasma norepinephrine (NE), serum TSH, free and total T4, and free and total T3 were repeated before and after 8 wk of exposure. TSH, free T4, and total T4 were 50% lower for T3+ than for T3- subjects. Total and free T3 were not different between groups. BMR was unchanged after habituation, whereas the cold-stimulated VO2, MAP, and NE were significantly reduced for all subjects in March. The relationship between VO2 and NE (r2 = 0.44, P less than 0.001) during the initial SCAT was unchanged with habituation. We suggest that human cold habituation is independent of major changes in circulating T4 and TSH.

scholarly journals Inhibition of pituitary type 2 deiodinase by reverse triiodothyronine does not alter thyroxine-induced inhibition of thyrotropin secretion in hypothyroid rats

2005 ◽  
Vol 153 (3) ◽  
pp. 429-434 ◽  
Author(s):  
P Cettour-Rose ◽  
T J Visser ◽  
A G Burger ◽  
F Rohner-Jeanrenaud
Keyword(s):  
Specific Inhibitor ◽  
Adult Rats ◽  
Reverse T3 ◽  
Brown Adipose ◽  
Tsh Secretion ◽  
Serum T3 ◽  
Serum T4 ◽  
Serum Tsh ◽  
Tsh Levels

Objectives: Intrapituitary triiodothyronine (T3) production plays a pivotal role in the control of TSH secretion. Its production is increased in the presence of decreased serum thyroxine (T4) concentrations and the enzyme responsible, deiodinase type 2 (D2), is highest in hypothyroidism. In order to document the role of this enzyme in adult rats we developed an experimental model that inhibited this enzyme using the specific inhibitor, reverse T3 (rT3). Methods: Hypothyroidism was induced with propylthiouracil (PTU; 0.025 g/l in drinking water) which in addition blocked deiodinase type 1 (D1) activity, responsible for the rapid clearance of rT3 in vivo. During the last 7 days of the experiment, the hypothyroid rats were injected (s.c.) for 4 days with 0.4 or 0.8 nmol T4 per 100 g body weight (bw) per day. For the last 3 days, the same amount of T4 was infused via s.c. minipumps. In additional groups, 25 nmol rT3/100 g bw per day were added to the 3-day infusion of T4. Results: Infusion of 0.4 nmol T4/100 g bw per day did not affect the high serum TSH levels, 0.8 nmol T4/100 g bw per day decreased them to 57% of the hypothyroid values. The infusions of rT3 inhibited D2 activity in all organs where it was measured: the pituitary, brain cortex and brown adipose tissue (BAT). In the pituitary, the activity was 27%, to less than 15% of the activity in hypothyroidism. Despite that, serum TSH levels did not increase, serum T4 concentrations did not change and the changes in serum T3 were minimal. Conclusions: We conclude that in partly hypothyroid rats, a 3-day inhibition of D2 activity, without concomitant change in serum T4 and minimal changes in serum T3 levels, is not able to upregulate TSH secretion and we postulate that this may be a reflection of absent or only minimal changes in circulating T3 concentrations.

Multiple cold air exposures change oral triiodothyronine kinetics in normal men

1992 ◽  
Vol 263 (1) ◽  
pp. E85-E93 ◽  
Author(s):  
H. L. Reed ◽  
M. M. D'Alesandro ◽  
K. R. Kowalski ◽  
L. D. Homer
Keyword(s):  
Cold Exposure ◽  
Volume Of Distribution ◽  
Metabolic Clearance ◽  
Group Effect ◽  
Metabolic Clearance Rate ◽  
Free T4 ◽  
Cold Air ◽  
Normal Men ◽  
Serum Tsh

The influence of cold exposure on triiodothyronine (T3) kinetics was studied in 16 men before, during (biweekly), and after 80 (10/wk) cold (4 degrees C) air exposures. We used serum values before and up to 24 h after a pharmacological oral (o) dose of T3 [76.8 nmol (50 micrograms)] to calculate noncompartmental kinetic parameters. To assess the role of thyroxine (T4) and thyrotropin (TSH), we administered a replacement dose of T3 [46.0 nmol/day (30 micrograms)] to eight men (+T3 group) and placebo to eight others (-T3 group) for the 2-mo study. There was no group effect of T3 treatment (+T3) on oral total volume of distribution (TVdo), metabolic clearance rate (MCRo), or disposal rate (DRo). TVdo was not changed over the study. Cold increased MCRo by 5.4 +/- 2.0 l.day-1.m-2. DRo increased with cold by 10.2 +/- 4.4 nmol.day-1.m-2. Although serum TSH, total T4, and free T4 decreased by approximately 50% in the +T3 group, the changes in MCRo and DRo with cold were not different from those in -T3. We describe that human T3 kinetics are changed with brief repeated exposures to cold air and that these increases in MCRo and DRo do not appear to be dependent on TSH or T4.

Republished: The relationship between serum TSH and free T4 in older people

2012 ◽  
Vol 88 (1045) ◽  
pp. 668-670 ◽  
Author(s):  
Penny M Clark ◽  
Roger L Holder ◽  
Sayeed M Haque ◽  
F D Richard Hobbs ◽  
Lesley M Roberts ◽  
...  
Keyword(s):  
Older People ◽  
Free T4 ◽  
The Relationship ◽  
Serum Tsh

scholarly journals The Effect of Droloxifene and Estrogen on Thyroid Function in Postmenopausal Women1

2000 ◽  
Vol 85 (11) ◽  
pp. 4407-4410
Author(s):  
Ellen Marqusee ◽  
Lewis E. Braverman ◽  
Jennifer E. Lawrence ◽  
Judith S. Carroll ◽  
Ellen W. Seely
Keyword(s):  
Postmenopausal Women ◽  
Treatment Period ◽  
Thyroid Function ◽  
Free T4 ◽  
Double Blind ◽  
Stimulatory Action ◽  
Serum Free ◽  
Serum T4 ◽  
Conjugated Estrogen ◽  
Serum Tsh

Estrogen is known to increase serum T4-binding globulin (TBG) concentrations, thereby increasing serum total T4 concentrations. Serum free T4 concentrations, however, remain normal. Tamoxifen, a selective estrogen receptor modifier (SERM), also raises serum TBG concentrations, but whether newer SERMs with less stimulatory action on the endometrium do so is not known. We, therefore, compared the effect of droloxifene, a SERM, and conjugated equine estrogen on pituitary-thyroid function in normal postmenopausal women. Ten women were treated for 6 weeks with conjugated estrogen (Premarin), 0.625 mg/day, and droloxifene, 60 mg/day, in a double-blind crossover study with an intervening 4-week no-treatment period. We measured serum T4, T3, TBG, free T4 index, and TSH at baseline and at the end of each 6-week period. The baseline values were compared with the 6-week values using paired t tests. The mean (±sd) serum TBG concentrations increased significantly during both treatment periods (baseline, 1.5 ± 0.4 mg/dL; conjugated estrogens, 2.7 ± 0.6 mg/dL; droloxifene, 2.1 ± 0.6 mg/dL; P < 0.001 and P= 0.001, respectively). There were no significant changes in the serum free T4 index. Serum T4 and T3 concentrations increased during both treatment periods, however, the increase was significant only for T4 during the conjugated estrogen treatment period. The serum TSH concentrations increased significantly during both treatment periods (18% during conjugated estrogen and 11% during droloxifene), and the values remained within the normal range in all women. Administration of both conjugated estrogen and droloxifene for 6 weeks increases serum TSH and TBG concentrations, but does not alter free T4 index values in postmenopausal women.

scholarly journals The Effect of Perchlorate, Thiocyanate, and Nitrate on Thyroid Function in Workers Exposed to Perchlorate Long-Term

2005 ◽  
Vol 90 (2) ◽  
pp. 700-706 ◽  
Author(s):  
Lewis E. Braverman ◽  
XueMei He ◽  
Sam Pino ◽  
Mary Cross ◽  
Barbarajean Magnani ◽  
...  
Keyword(s):  
Thyroid Function ◽  
Thyroid Volume ◽  
Production Plant ◽  
Sodium Iodide Symporter ◽  
Free T4 ◽  
High Exposure ◽  
Serum T4 ◽  
Serum Tsh ◽  
Serum And Urine

Perchlorate (ClO4−) and thiocyanate (SCN−) are potent and nitrate (NO3−) a weak competitive inhibitor of the thyroid sodium-iodide symporter. To determine the effects of long-term, high ClO4− exposure on thyroid function, we conducted a study of 29 workers employed for at least 1.7 yr (50% over 5.9 yr) in an ammonium ClO4− production plant in Utah. Serum ClO4−, SCN−, and NO3−; serum T4, free T4 index, total T3, thyroglobulin (Tg), and TSH; 14-h thyroid radioactive iodine uptake (RAIU); and urine iodine (I) and ClO4− were assessed after 3 d off (Pre) and during the last of three 12-h night shifts in the plant (During) and in 12 volunteers (C) not working in the plant. Serum and urine ClO4− were not detected in C; urine ClO4− was not detected in 12 of 29 and was 272 μg/liter in 17 Pre workers; serum ClO4− was not detected in 27 of 29 Pre; and serum and urine ClO4− were markedly elevated during ClO4− exposure to 868 μg/liter and 43 mg/g creatinine, respectively. Serum SCN− and NO3− concentrations were similar in all groups. Thyroid RAIUs were markedly decreased in During compared with Pre (13.5 vs. 21.5%; P < 0.01, paired t) and were associated with an increase in urine I excretion (230 vs. 148 μg I/g Cr; P = 0.02, paired t) but were similar to those in the C group (14.4%). Serum TSH and Tg concentrations were normal and similar in the three groups. Serum T4 (8.3 vs. 7.7 μg/dl), free T4 index (2.4 vs. 2.2), and total T3 (147 vs. 134 ng/dl) were slightly but significantly increased in the During vs. Pre workers (P < 0.01, paired t). Thyroid volumes and patterns by ultrasound were similar in the 29 workers and 12 community volunteers. In conclusion, high ClO4− absorption during three nights work exposure decreased the 14-h thyroid RAIU by 38% in ClO4− production workers compared with the RAIU after 3 d off. However, serum TSH and Tg concentrations and thyroid volume by ultrasound were not affected by ClO4−, suggesting that long-term, intermittent, high exposure to ClO4− does not induce hypothyroidism or goiter in adults.

scholarly journals Age and the Thyrotropin Response to Hypothyroxinemia

2010 ◽  
Vol 95 (8) ◽  
pp. 3675-3683 ◽  
Author(s):  
Rebecca Over ◽  
Sonia Mannan ◽  
Hala Nsouli-Maktabi ◽  
Kenneth D. Burman ◽  
Jacqueline Jonklaas
Keyword(s):  
Age Groups ◽  
Primary Hypothyroidism ◽  
Age Group ◽  
Older Individuals ◽  
Free T4 ◽  
Pathological Alteration ◽  
The Mean ◽  
The Relationship ◽  
Two Populations ◽  
Serum Tsh

Context: Some studies suggest altered pituitary functioning and TSH production with aging. Objective: Our objective was to test the hypothesis that less TSH production occurs despite comparable hypothyroxinemia with advancing age. Design: We retrospectively studied adult outpatients of all ages with confirmed hypothyroidism and documented their TSH and free T4 concentrations. Participants: Two populations of 112 patients were subdivided into four age groups: 1) patients newly diagnosed with primary hypothyroidism and 2) thyroid cancer patients undergoing l-T4 withdrawal in preparation for diagnostic or therapeutic radioiodine. Main Outcome Measure: The relationship between paired free T4 and TSH concentrations and patient age was studied. Results: With spontaneous hypothyroidism, the mean TSH concentration decreased nonsignificantly in each ascending age group with comparable free T4 (FT4) concentrations (<35 yr, 69 mIU/liter; 35–49 yr, 49 mIU/liter; 50–64 yr, 43 mIU/liter; >64 yr, 29 mIU/liter). With iatrogenic hypothyroidism, the mean TSH concentration decreased significantly in each ascending age group (<35 yr, 156 mIU/liter; 35–49 yr, 115 mIU/liter; 50–64 yr, 74 mIU/liter; >64 yr, 46 mIU/liter; P < 0.001) despite similar FT4 concentrations. The relationship between the log-transformed TSH and FT4 was significantly and inversely affected by age in multivariate analyses in both spontaneous hypothyroidism (P = 0.0005) and in iatrogenic hypothyroidism (P < 0.0001). Conclusions: Age modifies the pituitary set point or response to comparably reduced free T4 concentrations, resulting in lesser serum TSH elevation in older individuals. This phenomenon occurs with both spontaneous and iatrogenic hypothyroidism. This may be an adaptive response in normal aging or a pathological alteration of pituitary function with age.

Human thermoregulatory responses to cold air are altered by repeated cold water immersion

1986 ◽  
Vol 60 (5) ◽  
pp. 1542-1548 ◽  
Author(s):  
A. J. Young ◽  
S. R. Muza ◽  
M. N. Sawka ◽  
R. R. Gonzalez ◽  
K. B. Pandolf
Keyword(s):  
Cold Acclimation ◽  
Cold Water ◽  
Water Immersion ◽  
Stress Test ◽  
Cold Water Immersion ◽  
Plasma Norepinephrine ◽  
Cold Air ◽  
Thermoregulatory Responses ◽  
Before And After ◽  
C 30

The effects of repeated cold water immersion on thermoregulatory responses to cold air were studied in seven males. A cold air stress test (CAST) was performed before and after completion of an acclimation program consisting of daily 90-min cold (18 degrees C) water immersion, repeated 5 times/wk for 5 consecutive wk. The CAST consisted of resting 30 min in a comfortable [24 degrees C, 30% relative humidity (rh)] environment followed by 90 min in cold (5 degrees C, 30% rh) air. Pre- and postacclimation, metabolism (M) increased (P less than 0.01) by 85% during the first 10 min of CAST and thereafter rose slowly. After acclimation, M was lower (P less than 0.02) at 10 min of CAST compared with before, but by 30 min M was the same. Therefore, shivering onset may have been delayed following acclimation. After acclimation, rectal temperature (Tre) was lower (P less than 0.01) before and during CAST, and the drop in Tre during CAST was greater (P less than 0.01) than before. Mean weighted skin temperature (Tsk) was lower (P less than 0.01) following acclimation than before, and acclimation resulted in a larger (P less than 0.02) Tre-to-Tsk gradient. Plasma norepinephrine increased during both CAST (P less than 0.002), but the increase was larger (P less than 0.004) following acclimation. These findings suggest that repeated cold water immersion stimulates development of true cold acclimation in humans as opposed to habituation. The cold acclimation produced appears to be of the insulative type.

The relationship between serum TSH and free T4 in older people: Figure 1

2012 ◽  
Vol 65 (5) ◽  
pp. 463-465 ◽  
Author(s):  
Penny M Clark ◽  
Roger L Holder ◽  
Sayeed M Haque ◽  
F D Richard Hobbs ◽  
Lesley M Roberts ◽  
...  
Keyword(s):  
Older People ◽  
Free T4 ◽  
The Relationship ◽  
Serum Tsh

scholarly journals Is the Thyrotropin-Releasing Hormone Test Necessary in the Diagnosis of Central Hypothyroidism in Children

2003 ◽  
Vol 88 (12) ◽  
pp. 5696-5703 ◽  
Author(s):  
Ameeta Mehta ◽  
Peter C. Hindmarsh ◽  
Richard G. Stanhope ◽  
Caroline E. Brain ◽  
Michael A. Preece ◽  
...  
Keyword(s):  
Pituitary Hormone ◽  
Test Results ◽  
Trh Test ◽  
Free T4 ◽  
Central Hypothyroidism ◽  
Basal Serum ◽  
Serum T4 ◽  
The Mean ◽  
Test Increase ◽  
Serum Tsh

Abstract To determine the value of the TRH test, we analyzed the unstimulated serum T4 and TSH concentrations in 54 children with central hypothyroidism. A TRH test was performed in 30 patients. Midline brain defects (septo-optic dysplasia, 28; holoprosencephaly, 2) and combined pituitary hormone deficiencies were present in 30 and 52 patients, respectively. The mean serum free T4, total T4, and basal TSH concentrations were 0.6 ng/dl, 4.0 μg/dl, and 2.8 μU/ml, respectively. Five patients demonstrated elevated basal serum TSH concentrations. A normal TRH test [increase (Δ) in TSH, 4.5–17.8], based on data from 30 controls, was documented in 23.3% of patients. Brisk (ΔTSH, >17.8), absent/blunted (ΔTSH, <4.5), and delayed responses were documented in 16.7%, 30%, and 30% of patients, respectively. The mean age at diagnosis was 2.8 yr, with 8 patients evolving into TSH deficiency. It was not possible to differentiate patients as having pituitary or hypothalamic disease based solely on the TRH test results. Patients with septo-optic dysplasia were diagnosed earlier and had elevated basal serum TSH and PRL concentrations, diabetes insipidus, and evolving disease. Although full pituitary function assessment is mandatory to identify combined pituitary hormone deficiencies, a TRH test is not essential, and the diagnosis should be made by serial T4 measurements.

Enhancing Spatial Ability Through Sport Practice

2012 ◽  
Vol 33 (2) ◽  
pp. 83-88 ◽  
Author(s):  
David Moreau ◽  
Jérome Clerc ◽  
Annie Mansy-Dannay ◽  
Alain Guerrien
Keyword(s):  
Mental Rotation ◽  
Spatial Representations ◽  
Mental Rotation Test ◽  
Sport Training ◽  
Sport Practice ◽  
Undergraduate University Students ◽  
Before And After ◽  
Cognitive Plasticity ◽  
Reported Data ◽  
The Relationship

This experiment investigated the relationship between mental rotation and sport training. Undergraduate university students (n = 62) completed the Mental Rotation Test ( Vandenberg & Kuse, 1978 ), before and after a 10-month training in two different sports, which either involved extensive mental rotation ability (wrestling group) or did not (running group). Both groups showed comparable results in the pretest, but the wrestling group outperformed the running group in the posttest. As expected from previous studies, males outperformed women in the pretest and the posttest. Besides, self-reported data gathered after both sessions indicated an increase in adaptive strategies following training in wrestling, but not subsequent to training in running. These findings demonstrate the significant effect of training in particular sports on mental rotation performance, thus showing consistency with the notion of cognitive plasticity induced from motor training involving manipulation of spatial representations. They are discussed within an embodied cognition framework.

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