Cycles annuels de la testostéronémie et de la thyroxinémie chez Vipera berus L. (Reptilia: Viperidae) en relation avec le cycle sexuel et l'hivernage

1988 ◽  
Vol 9 (1) ◽  
pp. 33-42 ◽  
Author(s):  
François Fleury ◽  
Guy Naulleau
Keyword(s):  
Seasonal Variations ◽  
Secondary Peak ◽  
Plasma Testosterone ◽  
Maximal Concentration ◽  
Mating Period ◽  
Blood Samples ◽  
Vipera Berus ◽  
Testosterone Levels

AbstractBlood samples were taken in Vipera berus during a five year period. Changes in plasma thyroxine and testosterone levels were examined. Plasma testosterone levels show a marked profile. Highest levels are observed a few weeks after the emergence of hibernation from the end of March till the end of April. These values coincide with the mating period and spring spermiogenesis. Plasma thyroxine levels show also seasonal variations. Low values are observed in winter. Plasma thyroxine levels increase in spring and reach a maximal concentration shortly after the peak of plasma testosterone. A secondary peak is observed at the end of summer.

scholarly journals Testosterone is associated with harem maintenance ability in free-ranging grey-headed flying-foxes, Pteropus poliocephalus

2009 ◽  
Vol 5 (6) ◽  
pp. 758-761 ◽  
Author(s):  
Stefan M. Klose ◽  
Justin A. Welbergen ◽  
Elisabeth K. V. Kalko
Keyword(s):  
Plasma Testosterone ◽  
Flying Foxes ◽  
Mating Period ◽  
Social Challenges ◽  
Testosterone Levels ◽  
Harem Size ◽  
Pteropus Poliocephalus ◽  
Original Size ◽  
Complex Forms ◽  
Free Ranging

Males of many vertebrate species aggressively defend their reproductive interests by monopolizing females, and the ‘challenge hypothesis’ predicts that testosterone levels in reproductive contexts rise to facilitate males' competitive behaviours necessary for meeting social challenges. The hypothesis is successful in explaining patterns of testosterone secretion in many avian species, but remains comparatively unexplored in mammals. ‘Circulating plasma testosterone levels (T)’ were studied in relation to harem maintenance in grey-headed flying-foxes, Pteropus poliocephalus . In this species, harems provide mating opportunities and so a male's ability to maintain a harem is likely to correlate with his fitness. We hypothesized that if T reflect a male's ability to withstand challenges from competitors, then T should be linked to successful harem maintenance. To test this, we temporarily removed males from their territories prior to and during the short mating period, recording their harem sizes both before removal and after reintroduction. Most males successfully reclaimed their territory and a harem, but during the mating period, males with higher T had harems closer to their original size, and males with lower T suffered reduction in harem size. Our findings highlight the role of T in harem maintenance in a major mammalian taxon with complex forms of social organization.

PLASMA TESTOSTERONE LEVELS IN INTACT AND HEMICASTRATED GROWING COCKERELS

1979 ◽  
Vol 81 (2) ◽  
pp. 169-174 ◽  
Author(s):  
F. J. M. DRIOT ◽  
M. DE REVIERS ◽  
J. WILLIAMS
Keyword(s):  
Plasma Testosterone ◽  
Early Age ◽  
Blood Samples ◽  
Testosterone Levels ◽  
Testosterone Secretion ◽  
Testicular Hypertrophy

Changes in the levels of testosterone in plasma were measured by radioimmunoassay in blood samples taken at frequent intervals between 2 and 26 weeks of age from entire cockerels and cockerels hemicastrated before 2 weeks of age. In both groups the pattern of testosterone secretion could be divided into three clearly defined phases. In young birds, the levels of testosterone in plasma were low (0·3 ng/ml) but in the prepubertal period, at 11 weeks of age, they started to rise and continued to rise until 22 weeks of age when adult levels, which fluctuated between 2·5 and 3·5 ng/ml, were reached. In the immediate period after hemicastration, the concentration of testosterone decreased temporarily. From 11 weeks of age the levels of testosterone in the hemicastrated birds were approximately 75% of those in intact birds. These results are discussed in relation to the compensatory testicular hypertrophy which occurs in growing cockerels hemicastrated at an early age.

Seasonal variations in thyroxine and testosterone levels in relation to the moult in the adult male mink (Mustela vison Peale and Beauvois)

1981 ◽  
Vol 59 (6) ◽  
pp. 1062-1066 ◽  
Author(s):  
L. Boissin-Agasse ◽  
D. Maurel ◽  
J. Boissin
Keyword(s):  
Seasonal Change ◽  
Adult Male ◽  
Seasonal Variations ◽  
Environmental Temperature ◽  
Plasma Testosterone ◽  
Natural Light ◽  
Annual Maximum ◽  
Molting Cycle ◽  
Testosterone Levels ◽  
Ad Libitum

Plasma thyroxine (T4) and testosterone concentrations were measured in adult male mink maintained outdoors under natural light and fed ad libitum the whole year round. Plasma T4 concentrations presented a biphasic seasonal change, the highest values occurring in the spring and autumn months and the lowest values in the winter months. The plasma testosterone cycle showed an annual maximum in January–February. The possibility of testis–thyroid interactions is discussed. The changes observed are correlated with environmental temperature, photoperiod, and molting cycle.

PLASMA TESTOSTERONE LEVELS FOLLOWING SURGICAL STRESS IN MALE PATIENTS

1970 ◽  
Vol 65 (1) ◽  
pp. 11-17 ◽  
Author(s):  
K. Matsumoto ◽  
K. Takeyasu ◽  
S. Mizutani ◽  
Y. Hamanaka ◽  
T. Uozumi
Keyword(s):  
Postoperative Period ◽  
Plasma Levels ◽  
Surgical Stress ◽  
Control Level ◽  
Major Surgery ◽  
Plasma Testosterone ◽  
Blood Samples ◽  
Testosterone Levels ◽  
Competitive Protein Binding ◽  
Male Patients

ABSTRACT Plasma testosterone levels were determined by the competitive protein binding method of Mayes & Nugent (1968) with slight modifications, in 20 male patients in whom moderate or major surgery had been performed. Preoperative (control) and postoperative blood samples were obtained at 8 a. m. except for immediate postoperative samples. There was a significant decrease in the plasma levels of testosterone immediately and 2 days after moderate and major surgery. The level of testosterone returned toward the control level on the sixth postoperative day after moderate surgery, while after major surgery, the decreased plasma testosterone was maintained for at least 6 days. It is suggested that testicular secretion of testosterone seems to decrease during the postoperative period.

scholarly journals Changes in the Responsiveness of the Hypothalamic-Pituitary-Gonadal Axis to Kisspeptin-10 Administration during Pubertal Transition in Boys

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Ghulam Nabi ◽  
Hamid Ullah ◽  
Suliman Khan ◽  
Fazal Wahab ◽  
Pengfei Duan ◽  
...  
Keyword(s):  
Clinical Trial ◽  
Stage Iv ◽  
Tanner Stage ◽  
Plasma Testosterone ◽  
Clinical Trial Registration ◽  
Blood Samples ◽  
Testosterone Levels ◽  
Adult Men ◽  
The Mean ◽  
Pubertal Transition

In human, no studies are available regarding changes in kisspeptin1 receptor (KISS1R) sensitivity during pubertal transition. In this study, healthy boys were classified into 5 Tanner stages of puberty (n=5/stage). Human kisspeptin-10 was administered to boys at each Tanner stage and to adult men (n=5) as an IV bolus for comparison. Serial blood samples were collected for 30 min pre- and 120 min post-kisspeptin injection periods at 30 min interval for measuring plasma LH and testosterone levels. There was insignificant effect of kisspeptin on LH and testosterone levels in boys of Tanner stages I–III. At Tanner stage IV, the effect of kisspeptin on plasma LH was insignificant. However, a paired t-test on a log-transformed data showed a significant (P<0.05) increase in mean peak post-kisspeptin testosterone level. In Tanner stage V, a significant (P<0.05) increase was observed in mean post-kisspeptin peak LH level as compared to the mean basal LH value. Post-kisspeptin plasma testosterone levels were also significantly (P<0.05) increased as compared to the pre-kisspeptin level in Tanner stage V. Our data suggest that sensitivity of KISS1R on GnRH neurons with reference to LH stimulation in boys develops during the later part of puberty reaching to adult level at Tanner stage V. This trial is registered with WHO International Clinical Trial Registration ID NCT03286517.

INFLUENCE OF METYRAPONE ON PLASMA CONCENTRATIONS OF TESTOSTERONE AND ANDROSTENEDIONE IN MAN

1971 ◽  
Vol 68 (3) ◽  
pp. 576-584 ◽  
Author(s):  
K. O. Nilsson ◽  
B. Hökfelt
Keyword(s):  
Body Weight ◽  
Male Patient ◽  
Gradual Increase ◽  
Plasma Concentrations ◽  
Plasma Testosterone ◽  
Testosterone Levels ◽  
Basal Plasma ◽  
Normal Males ◽  
A Minor ◽  
Secondary Hypogonadism

ABSTRACT Metyrapone was administered either orally, 750 mg every four h, in a total of six doses, or intravenously 30 mg per kg body weight as a four h infusion. In three males with normal endocrine functions, metyrapone given orally or intravenously induced a fall in plasma testosterone and an elevation of androstenedione within 2–8 h. When metyrapone was administered to a patient given dexamethasone to suppress endogenous ACTH production, the androstenedione levels did not alter whereas the testosterone levels showed a slight, transient decrease. In two normal females metyrapone administration was followed by a marked increase in plasma androstenedione whereas testosterone showed only a minor, gradual increase. In one male patient with Addison's disease the basal plasma testosterone was normal whereas the level of androstenedione was low. Following metyrapone intravenously, there was a slight suppression of plasma testosterone but no change in the androstenedione concentration. In one patient with primary hypogonadism, two with secondary hypogonadism and two with Klinefelter's syndrome the plasma testosterone was low under basal conditions and did not change following metyrapone. Basal plasma androstenedione was within the range for normal males and increased markedly following metyrapone in all the cases.

Effects of oestradiol benzoate (OeB) and human chorionic gonadotrophin (hCG) on the testes and accessory sex glands of the rat

1981 ◽  
Vol 96 (2) ◽  
pp. 273-280 ◽  
Author(s):  
Mridula Chowdhury ◽  
Robert Tcholakian ◽  
Emil Steinberger
Keyword(s):  
Treated Group ◽  
Inhibitory Effect ◽  
Male Rats ◽  
Plasma Testosterone ◽  
Control Group ◽  
Intact Male ◽  
Intact Control ◽  
Testosterone Levels ◽  
Oestradiol Benzoate ◽  
Direct Inhibitory Effect

Abstract. It has been suggested that treatment of intact male rats with oestradiol benzoate (OeB) causes an interference with testosterone (T) production by the testes by a direct inhibitory effect on steroidogenesis. To test this hypothesis, different doses (5, 10 or 25 IU) of hCG were administered concomitantly with 50 μg of OeB to adult intact or hypophysectomized male rats. The testicular and plasma testosterone, and serum hCG levels were determined. The sex accessory weights were recorded. In the intact OeB-treated group of animals, hCG stimulated both the secondary sex organs and plasma testosterone levels above the intact control group. However, in hypophysectomized animals, although plasma testosterone levels increased above that of intact controls, their secondary sex organ weights did not. Moreover, inspite of high circulating hCG levels, the testicular testosterone content and concentration remained suppressed in OeB-treated animals. The reason for such dichotomy of hCG action on OeB-treated animals is not clear at present.

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