Effect of restricted blood flow on exercise-induced hormone changes in healthy men

To test the influence of the accumulation of metabolites on exercise-induced hormone responses, plasma concentrations of cortisol, growth hormone (GH), insulin, testosterone, thyrotropin (TSH), free thyroxine (fT₄) and triiodothyronine (T₃) were compared during exercise performed under normal conditions (control) and under conditions of restricted blood flow of exercising leg muscles (ischaemia) in nine healthy young men. Blood supply was reduced by 15%–20% by the application of 50?mmHg external pressure over the exercising leg. During 45-min cycling exercise during ischaemia the increase in GH concentration was twice as large as under normal conditions. Despite the below-threshold exercise intensity for activation of the pituitary-adrenocortical system under normal exercise conditions ischaemic exercise elicited cortisol and T₃ responses (concentration increases of 83% and 9.5%, respectively). Ischaemic exercise attenuated the decrease of plasma insulin concentration found under normal conditions. The concentrations of testosterone, TSH and fT₄ were not changed significantly during exercise performed in either condition. The results support the suggested essential role of muscle metaboreceptors in the control of hormone responses during muscle activity.     

Metabolic alterations induced by chronic heat exposure in the rat: the involvement of thyroid function

The effects of chronic exposure to high environmental temperature (34°C) on T₄ production rate, foodintake, growth-rate and resting metabolic rate were investigated in adult male rats. This study was designed to examine the extent of variations and possible relationships between these parameters. As compared to control rats of the same body weight kept at 25°C, rats exposed to 34°C for 3–4 weeks exhibited a retarded growth-rate: 2.3 vs 4.0 g/day, a reduced food-intake: 15.2 vs 23.2 g/day, a decreased T₄ production-rate: 1.8 vs 2.7 g/day and a decreased oxygen consumption: 4.0 vs 5.4 ml/min. Heat-exposure altered the 4 parameters to a similar extent. T₄ supplementation (3 g/day) which induced a decrease in plasma TSH concentration, did not restore a normal growth-rate in heat-exposed rats. The decreased food-intake of the heat-exposed rats was not associated with any significant changes in the daily pattern of variations of liver glycogen content, or in the mean daily levels of blood glucose or insulin. The ratio T₃ to rT₃ in plasma was not altered by chronic heat exposure. When rats which had been chronically exposed to heat (25 days at 34°C) were exposed to 25°C, growth-rate, food-intake and oxygen consumption rapidly increased to control values whereas the rate of T₄ production remained low. It is concluded that (1) a decrease in thyroid hormone economy is not directly involved in the alterations of growth and energy expenditure in rats chronically exposed to heat, (2) heat exposure does not lead to the establishment of a fasted state resulting from a large reduction in voluntary food intake, (3) metabolic alterations induced by heat exposure are rapidly and completely reversible upon decreasing the environmental temperature.     

Altered hormonal response to short-term bicycle exercise in young men after prolonged physical strain,caloric deficit,and sleep deprivation

Summary The hormonal response to a standardized bicycle exercise test was studied in 11 male cadets exposed to a course of 107 h of continuous activity with less than 2 h sleep. The subjects expended about 8,600–11,000 kcal/24 h whereas their daily food intake contained only about 1,500 kcal. The exercise test was performed once 12 days before the course (control experiment) and on day 3 and day 5 during the course, always between 0700–0900 h.A two to six fold increase was seen in the resting levels of noradrenaline, adrenaline, dopamine, and growth hormone during the course whereas a decrease was observed for thyroxine, triiodothyronine, and prolactin. Cortisol increased on day 3 and then decreased to precourse levels on day 5.The response to the exercise test during the course for all catecholamines was a further increase aboye and proportional to the raisted resting levels. Growth hormone increased by about 6–8 g/l both before and during the course. During the exercise test, cortisol decreased before the course whereas it increased during the course. All plasma levels of cortisol were higher on day 3 than on day 5 and in the control experiment.The post-exercise insulin increase was reduced during the course corresponding to a reduction in blood glucose levels. Prolactin decreased during and after exercise in the control experiment, whereas on day 5 the opposite response was seen. No changes in the disappearance rate of different hormones were observed during the course.The present investigation has demonstrated that prolonged strain severely affects the resting plasma levels of different hormones as well as the endocrine response to a short-term physical exercise.Per Kristian Opstad is a fellow of the Norwegian Council of Science and the Humanities     

Hormonal changes in serum in young men during prolonged physical strain

Summary The endocrine response to severe physical strain including lack of sleep has been investigated in army personnel during a combat course of 5 days' duration. The thyroxine (T₄) concentration in serum increased during the first 24 h, and then declined at a rate corresponding to a halflife of 7.6 days and on day 6 reached the lowest level, 55 ng/ml. Triiodothyronine (T₃) displayed a similar pattern, although an increase during the first 24 h could not be demonstrated. Within 48 h after the course T₄ had returned to normal, whereas the serum level of T₃ was significantly below the level before the course (p<0.05). The serum level of TSH was suppressed during the course.The serum level of prolactin was significantly suppressed and growth hormone was markedly elevated during the course with a significant negative correlation (r=–0.6) between the two. In agreement with a previous report, there was a rapid and sustained suppression of the serum level of testosterone to a mean level of 1.1 ng/ml on day 5.Short periods of sleep (3–6 h) were shown to be effective in reversing the changes described in this paper, especially for growth hormone, prolactin, and testosterone.This study represents a part of a research programme by the Stress Research Group of the Norwegian Joint Medical Services     

The TRH stimulation test in endemic goitre in Greece

Summary The serum T₄=T₄(D), T₃ in vitro uptake=RT₃U and TSH were measured before and 30 min after the injection of 200 µg of TRH in 30 subjects from an iodine deficient area of Central Greece. These persons were divided in two groups of 16 goitrous and 14 nongoitrous patients and the results from each group compared to each other and also with the same parameters obtained from 14 controls subjects, all nongoitrous and from a nonendemic area. It has been found that in this area with a mild iodine deficiency serum T₄ is the only hormone decreased whereas RT₃U and TSH both before and 30 min after TRH injection are normal. There existed however a negative correlation between serum T₄ and TSH in the goitrous group. Why the nongoitrous iodine deficient persons achieve the same compensation without thyroid gland enlargement remains unresolved but it may be stated from the present results that goitre development should be regarded as a maladaptation rather than a compensatory process.This work was supported by the Hellenic Ministry of Social Services.     

Thyroid function during a prolonged stay in Antarctica

Adaptation of the thyroid gland to the Antarctic environment was studied in nine healthy euthyroid tropical men of the Sixth Indian Antarctic Expedition during 1 year of their residence at polar latitudes. Circulatory concentrations of thyroid hormones, total T₄ (TT₄), total T₃ (TT₃), free T₄ (FT₄), free T₃ (FT₃), reverse T₃ (rT₃), thyroxine binding globulin. (TBG), T₃ uptake and thyroid stimulating hormone (TSH) were estimated in New Delhi and during the first week of each month of the stay in Antarctica. At the end of the Austral summer in March, the TT₃ concentrations were found to be significantly lower (P < 0.01) compared to values recorded in New Delhi and showed a significant increase (P < 0.05) during the Austral winter in August. The mean TT₃ concentrations from May to December were found to be significantly higher than the March or April values. Plasma TT₄ and rT₃ concentrations tended to decline in March but remained unaltered during the entire period in Antarctica. The FT₄, FT₃, TBG and T₃ uptake did not show any appreciable change. Though, the TT₃ : TT₄ ratio tended to decline in March and April suggesting decreased peripheral conversion of T₄ to T₃ as the possible mechanism for a decline in TT₃ in March, physical exertion and prolonged exposure to extreme cold appeared to be the major contributory factors. The TSH concentration in March, April, November and December were found to be significantly higher than the New Delhi values. The morning as well as evening cortisol concentrations during the Austral winter were higher than the March values suggesting that cortisol rhythmicity was well maintained in Antarctica, albeit at a higher level. These observations indicated that the subtle changes in thyroid hormones during a prolonged stay at polar latitudes are related not only to the extreme cold but also to other factors such as physical activity, polar days and polar nights.     

Seasonal changes in circadian rhythms of body temperatures in humans living in a dry tropical climate

Summary Seven volunteers (3 females and 4 males; 3 Caucasians and 4 Africans) participated in two 24 h sessions during the cool dry (CD) and the hot dry (HD) seasons of the sahelian tropical climate. Body temperatures were taken on portable cassette recorders for 24 h. Rectal (T _re) and mean skin (¯T _sk) temperatures decreased in the HD compared to the CD conditions, meeting one of the criteria for adaptation to heat. No ethnic differences in thermal responses were found. Males and females differed in their body temperature rhythms and in their reactions to heat. Body temperatures were higher in females than in males. Males reacted to heat with a decrease in T _re, without change in the T _re-¯T _sk gradient. Females showed a decrease in both T _re and ¯T _sk, more marked for ¯T _sk, with an increase in the T _re-¯T _sk gradient. It was concluded that males showed seasonal acclimatization to heat via a decrease in metabolism confirmed by a decrease in plasma levels of thyroid stimulating hormone (TSH) in the HD condition. Females showed a mixed metabolic and thermolytic type of acclimatization, with an absence of variation in plasma TSH levels. In conclusion, the steady rise in temperature between the CD and HD conditions was sufficient to trigger an acclimatization to heat similar in Caucasian and African subjects, although exposure to the external climate differed widely.     

Preliminary results on mood state, salivary testosterone:cortisol ratio and team performance in a professional soccer team

Mood, as measured by the profile of mood states questionnaire (POMS), salivary cortisol (F) and testosterone (T) levels, and performance were examined in 17 male soccer players 4 times during a season. Soccer players provided three saliva samples when getting up (resting values, 8 a.m.), before breakfast (11.30 a.m.), and between 4.00p.m. and 6.00 p.m. The initial measures were performed 1 day following the start of season training (T₁). They were then performed before and after a high-intensity training programme (T₂ and T₃, respectively) and 16 weeks after T₃ (T₄). Iceberg profiles of POMS were observed during T₁, T₂ and T₃, which coincided with successful performance. Subsequent decreased performance between T₃ and T₄ coincided with a decrease in vigor and an increase in tension and depression. Indeed, when the normal nycthemeral rhythm for F was observed (i.e. a decrease from morning until evening at all times; T₁–T₄), there was seemingly a non-statistical elevation of F on the morning of T₃, which only became statistically significant at 11.30 a.m. on T₃. In spite of a post-high-intensity training programme (T₃) increase in catabolism, the soccer players presented iceberg profiles together with a high percentage of winning. Our results could suggest that in team soccer, a decreased T:F ratio does not automatically lead to a decrease in team performance or a state of team overtraining. It appears that combined psychological and physiological changes during high-intensity training are primarily of interest when monitoring training stress in relation to performance. Electronic Publication     

Ultrastructural and functional effects of chronic endogenous stimulation of thyroid cells by thyrotropin

Following total thyroidectomy, a small quantity of thyroid tissue was transplanted to the spleen in order to study thyroid tissue subjected to chronically elevated levels of endogenous thyrotropin (TSH). Plasma thyroxine (T₄) and TSH levels were monitored and correlated with ultrastructural studies of the tissue over a 32-week experimental period. The effects of administration of an iodine-poor diet, an exogenous acute dose of TSH, and suppression of endogenous TSH through thyroxine administration were studied in order to evaluate the plasticity of the experimental model. Plasma T₄ decreased after the first week and remained at approximately one half of the initial value until 12 weeks. Plasma TSH increased to a high of 6,220 ng/ml after 6 weeks and gradually declined to one half of that value. The transplanted tissue remained functional throughout the experimental period. The number of pseudopods decreased, and irregularly shaped, dense bodies increased from the time of surgery until 12 weeks later. Administration of an acute dose of TSH at this time resulted in obvious mitotic activity and the formation of numerous pseudopods. The tissue also maintained the ability to take up radioactive iodine and to iodinate thyroglobulin. Inhibition of TSH secretion through T₄ administration from the time of surgery did not affect viability. Some cellular hypertrophy persisted after 32 weeks although TSH and T₄ had returned to normal. This study has shown that thyroid tissue remains viable, functional, and experimentally alterable throughout an extended period of chronic stimulation by endogenous TSH, and that it has the reserve capacity to secrete normal levels of T₄ at the end of this experimental period.     

Thyroid function and thyroid hormone metabolism in elderly people low T3-syndrome in old age?

Summary T₄-, T₃- and reverse-T₃ concentrations were measured in the sera of 365 subjects beyond the age of 65 in order to evaluate if the decrease of serum T₃ frequently observed in old age can be attributed to old age per se or to concomitant non-thyroidal disease. The results obtained from a carefully selected healthy group of elderly people show that 1) total and free T₃ levels are lower in senescence but well within the range for euthyroidism in younger healthy controls; 2) the decrease of serum T₃ is more pronounced and occurs earlier in healthy old males than in females, so that for subjects over the age of 75, the upper limit for euthyroidism has to be adjusted by 10% in women and by 20% in men; and 3) there is no low T₃ syndrome characterized by decreased serum T₃ and increased serum reverse T₃, solely due to old age.Turnover kinetics have shown the daily production of T₄ and T₃ in old age to decrease by 20 µg and 10 µg, respectively, and an increased T₃ metabolic clearance not to account for the reduction of serum T₃ concentrations. Combined stimulation tests with TSH and TRH showed that the functional reserve of the thyroid gland to produce T₃ is maintained in old age. The first step in the sequence of events may be seen in an impairment of TSH secretion leading to an adaptation of the amount of thyroid hormones to a reduced mass of metabolically active body tissue in old age.     

Nocturnal hormonal responses to resistance exercise

The effects of resistance exercise on the nocturnal responses of cortisol (CO), testosterone (TEST), human growth hormone (hGH), and thyroid hormones (T₃, T₄) were examined in eight trained weight lifters. Each subject completed two trials using a counterbalanced design: a control, no exercise trial (CON) and a heavy resistance exercise session of three sets of six exercises to exhaustion (RE). The exercise session took place between 1900 and 2000 hours. Blood was sampled prior to and at 20-min intervals after RE. For both trials blood was sampled at hourly intervals from 2100 hours until 0700 hours. The hGH and CO concentrations were increased up to 40-min post-exercise (P < 0.05), but returned to resting levels 1 h post-exercise. Nocturnal hGH concentration was not affected by RE (P > 0.26) and peaked at 0200 hours and declined until 0700 hours. Similarly, the CO responses were similar between the trails (P > 0.14). This CO concentrations declined from 2200 hours until 0100 hours, then increased steadily until 0700 hours. The TEST concentrations during both trials rose steadily from 2200 hours until 0700 hours; however, the rise in TEST from 0500–0700 hours during RE was greater than during the CON trails (P = 0.059). The T₃ concentrations were unchanged by exercise and were similar at all times between trails. The T₄ concentrations were elevated for 20 min after RE; however nocturnal T₄ concentrations were lower after RE than during CON. These results would suggest that bGH and CO may have limited nocturnal reactivity to resistance exercise. However, the nocturnal alterations of TEST and T4 after resistance exercise, although small, may have implications for muscle anabolism.     

Enzymatic and hormonal responses following a 24 h endurance run and a 10 h triathlon race

Summary Muscle cell leakage and hormonal changes were compared immediately after and during the 3 days following a 24 h endurance run (R_{24 h}) in 8 subjects, and a 10 h triathlon non-competitive race (T_{10 h}) in 6 subjects. The study showed three main differences: 1) plasma enzyme increases were considerably more significant in R_{24 h} than in T_{10 h}: compared with resting levels, creatine kinase increased ×120 after R_{24 h} but only ×2 after T_{10 h}; lactic dehydrogenase ×4, as opposed to ×1.5; and transaminases only showed an increase after R_{24 h}. The plasma myoglobin increase after R_{24 h} was double that found after T_{10 h}; 2) for the same magnitude of plasma aldosterone and cortisol after R_{24 h} and T_{10 h} (3 times the resting levels), a highly significant decrease in urinary Na⁺ (p<0.001) and an increase in urinary K⁺ (p<0.01) were found only after R_{24 h}; and 3) the plasma free noradrenaline level increased significantly after R_{24 h} (×2.6) whereas it was unchanged after T_{10 h}. In contrast, the plasma level of conjugated dopamine increased only after T_{10 h} (×3.7, p<0.05). These results suggest that long-distance running causes more muscular lesions than the triathlon, and that important factors other than aldosterone are probably involved in the regulation of urinary electrolyte excretions during T_{10 h}.     

TSH,T3, rT3 and fT4 in maximal and submaximal physical exercise

Summary The response of various thyroid hormone parameters to maximal physical exercise (MPE) was investigated in 14 medium and long distance runners and 13 divers. The effect of submaximal long time physical exercise (SMPE) was examined in seven divers. The TSH-level decreases significantly during MPE and slightly rises again after the end of the exercise. In SMPE, however, TSH continuously rises until 15 min after the end of the exercise. The T₃ level rises significantly in MPE and falls below the initial value 15 min after the exercise finishes, during SMPE it remains practically unchanged and slightly decreases after the finish. In MPE, the rT₃ level does not change and slightly decreases after termination, while the fT₄ level continuously decreases from the beginning till 15 min after the exercise period. The latter two parameters do not show any change in SMPE. As possible reasons for the changes of TSH levels a decrease (MPE) or an increase (SMPE) of pituitary secretion might play a role. Furthermore, in MPE the rise in T₃ level might be related to hemoconcentration, and the decrease in fT₄ level to an elevated cellular utilization.     

PRL,TSH, and thyroid hormones in benign breast diseases

Summary The dynamic secretion of prolactin and TSH as well as the thyroid function were studied in patients with benign breast disease. The study included 13 patients with mastodynia, 15 patients with isolated galactorrhea, 6 patients with breast hypertrophy and 5 patients with fibroadenomata. Eleven healthy women served as controls. Prolactin and TSH were determined before and after TRH stimulation, using 0.2 mg TRH i.v. In addition thyroxine (T₄), trijodthyronine (T₃) and thyroxin-binding-globulin (TBG) were estimated.The following results were obtained: Basal prolactin levels were slightly but not significantly elevated in all patients studied. Maximal prolactin response to TRH was significantly greater as compared to the controls. TSH, T₄, T₃, and TBG-levels in the controls were within the normal range, while mastodynia and galactorrhea patients exhibited hormone patterns as known from endemic goiter (increased T₃- and relatively low T₄-levels). Mean TSH-responses reached the upper limit of the normal range. Mean TBG-levels in mastodynia patients exceeded the levels of the controls. In patients with breast hypertrophy thyroid hormone status indicated borderline hypothyroidism (borderline T₄- and normal T₃-levels, mean TSH-response slightly elevated to TRH). TSH secretion and thyroid function in patients with fibroadenomata did not differ from the controls.The presented data indicate an increased sensitivity of the lactotrophs representing possibly an important factor in the development of these benign breast diseases. The thyroid function tests in these patients revealed patterns known from endemic goiter and borderline hypothyroidism respectively.     

Tubular transport processes in proximal tubules of hypothyroid rats. Lack of relationship between thyroidal dependent rise of isotonic fluid reabsorption and Na+−K+-ATPase activity

Hypothyroid rats reconstituted with 10 g/kg b.w. per day of tri-iodothironine (T₃) for 4 days resulted in normal free T₃ and TSH levels. FT₃ levels were: 0.53±0.3 pg/ml in hypothyroid rats; 2.78±1.21 pg/ml in hormone reconstituted rats and 2.90±0.90 pg/ml in euthyroid rats. TSH levels were 3,508±513 g/ml in hypothyroid rats; 1,008±204 g/ml in reconstituted rats and 270±184 ng/ml in euthyroid rats.When hypothyroid rats were reconstituted with 50 g T₃/kg b.w. per day, TSH levels were nearly normal after 4 days (1,157±621 ng/ml). However FT₃ levels after 1–4 days were always higher than in euthyroid rats.Hypothyroid rats show a decrease in isotonic fluid reabsorption (J _v) in the proximal tubule (1.50±0.08 versus 4.96±0.23 10^–2 nl·mm^–1·s^–1 in euthyroid animals). 1 day after T₃ (10 g/kg b.w./day) injectionJ _v was increased significantly to 2.05±0.20 10^–2 nl·mm^–1·s^–1 and continued to increase during 4 days of T₃ reconstitution.When 50 g T₃/kg b.w./day was used,J _v increased to 2.75±0.07 after 1 day and to 3.10±0.42 10^–2 nl·mm^–1·s^–1 after 4 days.J _v was never reaching a value close to that of euthyroid rats because the tubular radius in hypothyroid rats (14.7±1.8 m) is less than that of euthyroid rats (19.2±0.5 m). The radius in hypothyroid rats treated with T₃ was unchanged over a 4 day course with either high or low doses of T₃.Na⁺–K⁺-ATPase activity was found to be 2.91±0.16 M P_i/h×mg protein in homogenates of kidney cortex from hypothyroid rats. Treatment of hypothyroid rats with 10 g or 50 g of T₃ resulted in an initial decrease in ATPase activity, followed by an increase to base level in hypothyroid rats with 10 g and a significantly higher level with 50 g. This decrease in ATPase activity was contrasted to the increase inJ _v.These data indicate that there is a dissociation between the effects of physiological doses of thyroid hormones on proximal tubular reabsorption and the effects of T₃ on Na⁺–K⁺-ATPase activity of kidney cortex. This leads to question the relationship between sodium transport and ATPase activity under physiological doses of thyroid hormones. An early effect of physiological doses of thyroid hormones on brush border Na⁺ permeability is suggested.     

Dysregulation of calcium channels decreases parasecretion in pancreatic β-cells in rats born small for gestational age

Objective: To investigate the role of intrauterine malnourishment in the development and function of pancreatic islet β-cells. Methods: Whole-cell patch clamping was used to record voltage-gated calcium channel (VGCC)-mediated currents. Insulin secretion was detected by measuring capacitance using a sequence of sine wave stimuli. VGCC currents and insulin secretion were measured in the small for gestational age (SGA) group treated with human recombinant growth hormone (hGH). Results: The membrane capacitance in the SGA group (6.4?±?0.9?fF/Pf) was significantly reduced. Calcium current density and peak current density in the SGA group were also markedly decreased, whereas other measurements of calcium channels were unaltered. Treatment with hGH significantly rescued the membrane capacitance, whereas calcium channels were not affected. Conclusion: Our data suggest that decreased β-cell secretion is caused by a decreased expression of calcium channels and reduced calcium currents. hGH restores β-cell secretion in SGA animals, possibly independently of VGCC.     

Humoral and neurohormonal aspects of blood pressure regulation: Focus on angiotensin

Summary TSH, T₃ and T₄ response to stimulation with thyrotropin releasing hormone (TRH) has been investigated in 24 young healthy adults after intravenous injection and in 25 young healthy adults upon oral application of 40 mg of TRH. After intravenous injection the TSH concentration raises from a mean of 1.6 to a mean maximum of 11.7µU/ml. A statistically significant sex difference could not be found. T₃ shows a statistically significant increase which is however too small to be of diagnostic value in an individual test.After oral stimulation with 40 mg of TRH, TSH rises to a slightly higher maximum of 13.2 µU/ml after 3 h. The T₃ increase from 1.5 to 2.19 ng/ml is significant and considerably higher than after intravenous stimulation. The thyroxin increase is statistically significant.The present results compare well with previously published data for intravenous stimulation. The oral route of TRH application has not yet been widely used and the present series establishes the normal response in young healthy adults.Repetitive stimulation with three times 40 mg of TRH leads to a decrease in TSH stimulation which reaches 5.8 µU/ml 3 h after the third dose. This is in contrast to a comparable increase in plasma T₃.     

Hypothalamo-hypophysäre Schilddrüsen-Achse,Plasmaproteinkonzentrationen und die hypophysäre Gonaden-Achse im Low-T3-Syndrom nach akutem Myokardinfarkt (AMI)

Summary In patients with severely acute diseases, a special relationship of thyroidal hormones with decreased T3 and increased rT3 levels is known, the so-called low T3 syndrome. The aim of this study was to elucidate the involvement of the hypothalamo-pituitary thyroid axis, the pituitary-gonadal axis, the altered hepatic function, the plasma proteins in the low T3 syndrome, and the evaluation of these parameters for prognosis in patients with acute myocardial infarction. Thirty-one patients (29 male, 2 female) with AMI entered the study for the determination of hypothalamo-pituitary thyroid axis and the plasma proteins. Besides routine laboratory determinations, TRH, TSH, T4, T3, rT3, CHE, albumin, total protein, TBG, and estradiol concentrations in plasma were measured daily for 5 days after AMI using immunological and other methods. Twelve male patients with AMI entered the study for the determination of pituitary-gonadal axis; the T3, rT3, estradiol, testosterone, FSH, and LH concentrations in serum were determined using immunological methods. We found that T3 and T4 decreased significantly to a minimum on the first and the second day, respectively, after admission and increased in the course of the observation period. In contrast, rT3 was elevated significantly within the first 2 days and decreased later. TSH and TRH decreased in the first 2 days and increased in the following days. CHE, albumin, and total protein levels significantly showed a minimum on day 4 and TBG significantly showed a minimum on the second day after AMI and increased to day 4. The estradiol and testosterone levels were high on admission and decreased in the following days and increased again in the observation period. FSH decreased in the first 2 days and increased in the following course similar to estradiol and testosterone. Patients who died within 2 weaks after AMI showed a plasma hormonal pattern of hypothyroidism with low TSH levels and hypogonadotropic hypogonadism on the second day, whereas this pattern is persistent in the following days. These results show the involvement of the hypothalamo-pituitary axis in the low T3 syndrome and that characteristics for acute partial insufficiency of the anterior pituitary gland are signs of a bad prognosis. Whether Gn-RH and ACTH also decreased after AMI is unknown. The necessity for substitution is unclear and needs further investigation

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Abkürzungen HVL Hypophysenvorderlappen - AMI Akuter Myokardinfarkt - T3 Total-Trijodthyronin - T4 Total-Thyroxin - rT3 reverse-T3 - TRH Thyreotropin-Releasing Hormon - Gn-RH Gonadotropin-Releasing Hormon - CRF Corticotropin-Releasing Factor - TSH Thyreotropin - TBG Thyroxin-bindendes Globulin - FSH Follikelstimulierendes Hormon - LH Luteinisierendes Hormon - CPK Kreatin-Phospho-Kinase - x Mittelwert - SD Standardabweichung Herrn Professor Dr. K. Schöffling zum 65. Geburtstag gewidmet     

Screening for thyroid disorders in a working population

Summary Subclinical thyroid disorders have received increasing attention in recent years due to refined laboratory methods and a stronger emphasis on the role of preventive medicine. We performed a screening for thyroid-stimulating hormone (TSH) on 6884 persons in a working population. In cases in which TSH was not within the normal range we also measured the levels of triiodothyronine (T₃), thyroxine (T₄), and thyroxine-binding globulin (TBG). All persons who did not present with exclusion criteria or other nonthyroidal illnesses (n = 59) and the controls (n = 39) were submitted to thyrotropin-releasing hormone (TRH)-testing. Additionally, sonography of the thyroid was performed on 120 persons (59 subjects with abnormal hormone levels and 61 controls) to determine thyroid size and rule out morphological abnormalities. Based on the TRH test and T₃, T₄, and TBG measurements we found a prevalence of 0.03% (2/6884) for overt hyperthyroidism, 0.33% (23/6884) for subclinical hyperthyroidism, 0.09% (6/6884) for subclinical hypothyroidism, and 0.015% (1/6884) for overt hypothyroidism in the healthy population. In subjects with overt or subclinical hyperthyroidism the prevalence of goiters (thyroid volume > 18 ml in women, > 25 ml in men) was 28%. Of this group 48% had structural abnormalities. All persons with goiters and/or structural abnormalities were over 35 years of age. Among the euthyroid, 20% had thyroid enlargement, and the same proportion presented with structural abnormalities. There were no differences between the two age groups. In the group with overt/subclinical hypothyroidism 47% presented with structural abnormalities of the thyroid; however, none presented with thyroid enlargement. Thyroid nodules were found only in older persons (> > 35 years) with euthyroidism or hypothyroidism. These data confirm the relatively high prevalence of functional and morphological abnormalities of the thyroid. An early substitution with iodine is warranted to prevent functional and morphological disorders of the thyroid in older age. People with subclinical hyperthyroid disorders must avoid exposure to iodine, which can cause an exacerbation of the disease.Abbreviations TBG thyroxine-binding globulin - TRH thyrotropin-releasing hormone - TSH thyroid-stimulating hormone - T₃ triiodothyronine - T₄ thyroxine Dedicated to Prof. Dr. N. Zöllner on the occasion of his 70th birthday     

Changes in certain diurnal hormonal rhythms in developing male rats exposed to adiurnal environmental cues

It has traditionally been thought that diurnal rhythmicities cannot be entrained to follow adiurnal environmental cues that deviate greatly from a 24-hour periodicity. In this study, exposure of male rats pre- and postnatally to an adiurnal lighting schedule of 9 hours light: 9 hours dark resulted in the entrainment of certain hormonal rhythms (such as plasma corticosterone and plasma TSH) but not of others (such as pituitary TSH and plasma T₃). Even though thyroid rhythms were influences only partially by the shorter, 18-hour day, absolute levels of pituitary TSH and plasma T₃ were significantly higher in experimental rats (9 hours light:9 hours dark) than controls (12 hours light:12 hours dark). Whole-body and kidney weights and tail length were also significantly increased in the 9 hours light:9 hours dark animals, suggesting a possible relationship of shorter day cycles to faster growth and higher thyroid hormone levels.