scholarly journals Alterations in pituitary gland sensitivity in ram lambs to physiological doses of gonadotrophin-releasing hormone (GnRH), after divergent selection based on the luteinizing hormone response to a pharmacological GnRH challenge

Reproduction ◽  
1991 ◽  
Vol 93 (2) ◽  
pp. 559-567 ◽  
Author(s):  
N. P. Evans ◽  
J. R. McNeilly ◽  
A. J. Springbett ◽  
R. Webb
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Divergent Selection ◽  
Hormone Response ◽  
Releasing Hormone ◽  
Gonadotrophin Releasing Hormone ◽  
Ram Lambs

IN-VITRO STUDIES OF THE EFFECTS OF OESTROGEN PRETREATMENT ON THE SENSITIVITY OF THE IMMATURE FEMALE RAT PITUITARY GLAND TO STIMULATION WITH GONADOTROPHIN RELEASING HORMONE

1977 ◽  
Vol 74 (1) ◽  
pp. 11-21 ◽  
Author(s):  
M. WILKINSON ◽  
D. DE ZIEGLER ◽  
DANIELLE CASSARD ◽  
K. B. RUF
Keyword(s):  
Pituitary Gland ◽  
Brain Lesion ◽  
Culture Technique ◽  
Female Rats ◽  
Female Rat ◽  
Immature Female ◽  
Releasing Hormone ◽  
Gonadotrophin Releasing Hormone ◽  
Unilateral Brain Lesion

The effects of oestrogen priming on the sensitivity of the anterior pituitary gland to stimulation with gonadotrophin releasing hormone (GnRH) was investigated in immature female rats using a new organ culture technique. Hemipituitary glands obtained from animals primed with a single dose of oestradiol benzoate (OB; 20 μg/100 g body weight) released significantly more LH when pulsed with GnRH (4 nmol/l) than did control hemipituitary glands. This potentiating effect was detectable as early as 5 days after birth. After a second stimulation, LH secretion remained high. These results were compared with those obtained from animals treated to induce increased levels of endogenous oestrogen on day 26 of life. Thus, hemipituitary glands were obtained from animals given two injections of OB, an injection of pregnant mare serum gonadotrophin (PMSG) or a unilateral brain lesion placed in the basal hypothalamus. Pituitary tissue was stimulated as before with a pulse of GnRH. Two injections of OB enhanced the sensitivity to stimulation. Conversely, both PMSG and lesion treatment severely reduced the sensitivity to GnRH, although PMSG-treated and lesioned animals have been used as models for the study of ovulation.

Decreased serum testosterone and free triiodothyronine levels in healthy middle-aged men indicate an age effect at the pituitary level

1995 ◽  
Vol 132 (6) ◽  
pp. 663-667 ◽  
Author(s):  
Eva Marie T Erfurth ◽  
Lars E Hagmar
Keyword(s):  
Luteinizing Hormone ◽  
Young Men ◽  
Serum Testosterone ◽  
Free Testosterone ◽  
Age Effect ◽  
Hormone Response ◽  
Middle Aged ◽  
Free Triiodothyronine ◽  
Thyrotrophin Releasing Hormone ◽  
Releasing Hormone

Erfurth EMT, Hagmar LE. Decreased serum testosterone and free triidothyronine levels in healthy middle-aged men indicate an age effect at the pituitary level. Eur J Endocrinol 1995;132:663–7. ISSN 0804–4643 In an attempt to study further the age-specific influence on the hypothalamo-pituitary–gonadal axis as well as the hypothalamo–pituitary–thyroid axis, we have now investigated young and middle-aged men, considering possible confounding factors. Both serum total testosterone, free testosterone and the total ratio of testosterone to sex-hormone binding globulin were significantly lower among middle-aged men as compared with young men (p = 0.02, p = 0.002 and p = 0.0003, respectively). In accordance with these findings there was also a decrease in the luteinizing hormone response to gonadotrophin-releasing hormone in the middle-aged men (p= 0.02). Free testosterone was correlated significantly with the luteinizing hormone response (r = 0.32, p = 0.02). Serum free triiodothyronine was significantly higher among young men as compared with middle-aged men (p = 0.002) and the thyrotrophin-releasing hormone-stimulated thyrotrophin response was also higher in the young group compared with the middle-aged group. The present results may indicate that the age effect on serum levels of testosterone and free triidothyronine is mediated at the pituitary level. Eva Marie Erfurth, Dept. of Internal Medicine, University of Lund, S-221 85 Lund, Sweden

Sign in / Sign up

Export Citation Format

Share Document