Age-related alterations in gonadotropin, adrenocorticotropin and growth hormone secretion

1992 ◽  
Vol 4 (2) ◽  
pp. 103-113 ◽  
Author(s):  
Daniela Cocchi
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Age Related

Transgenic growth hormone mice exposed to lifetime constant illumination: gender-specific effects

2004 ◽  
Vol 82 (6) ◽  
pp. 950-965 ◽  
Author(s):  
M L Perreault ◽  
C D Rollo
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Control Group ◽  
Differential Growth ◽  
Lower Growth ◽  
Laboratory Rats ◽  
Specific Effects ◽  
Age Related ◽  
Gender Specific

Photoperiod affects most of the features altered in transgenic growth hormone (TG) mice, and laboratory rats and mice retain some sensitivity to photoperiod. We examined growth, feeding, longevity, and reproduction of TG mice and normal control mice (Mus musculus L., 1758) in 12 h light : 12 h dark (LD) and 24 h light (LL) photoperiods. Sexual dichotomy in growth and hepatic gene expression are considered to require gender-specific patterns of growth hormone secretion that are absent in TG mice. Regardless, in the LD photoperiod mature TG females were 82.8% (46.8 g) of the mass of TG males (56.5 g, p < 0.05), whereas control mice showed no size dichotomy (≈33 g). Mature masses of TG males and of control mice of either gender were unaffected by the LL photoperiod. TG females, however, reached a mature mass 92% (50.9 g) of that of mature TG males in the LL photoperiod, attenuating the sexual size dichotomy expressed in the LD photoperiod. Growth of females was slower than that of males, even in the control group. TG females in the LL photoperiod expressed faster growth, higher reproduction, and greater mean longevity than TG females in the LD photoperiod. Differences in age-related feeding associated with gender and photoperiod reflected differential growth rates. Females grew more slowly and ate more than males of similar age because they were smaller (i.e., had lower growth efficiencies). The LL photoperiod improved the energy balance of TG females. Possible mechanisms mediating such gender-specific effects are explored.

Age-related blunting of growth hormone secretion during exercise may not be solely due to increased somatostatin tone

Metabolism ◽  
1999 ◽  
Vol 48 (5) ◽  
pp. 665-670 ◽  
Author(s):  
Taylor J. Marcell ◽  
Robert A. Wiswell ◽  
Steve A. Hawkins ◽  
Kyle M. Tarpenning
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Age Related

Negative feedback of insulin-like growth factor-I on growth hormone secretion by porcine pituitary cells

1995 ◽  
Vol 75 (1) ◽  
pp. 57-61 ◽  
Author(s):  
C. Farmer ◽  
H. Lapierre
Keyword(s):  
Growth Hormone ◽  
Negative Feedback ◽  
Culture Media ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Late Gestation ◽  
Pituitary Cells ◽  
Gh Secretion ◽  
Age Related ◽  
Igf I

Pituitaries from female Yorkshire pig fetuses (90 d, n = 26; 110 d, n = 17) and 6-mo-old pigs (n = 5) were enzymatically dispersed, plated, and cultured for 47 h. The cells were then rinsed and incubated for 22 h with testing media containing 0, 50, 100, 200, 300 or 400 ng mL−1 of IGF-I. Half of the wells from each concentration of IGF-I were then incubated for an additional 3 h with concentrations of IGF-I similar to those in the previous incubation, while the other half also had GRF added to the testing media to reach a final concentration of 10−8 M. Culture media were then collected from all the wells, were frozen, and later assayed for GH. Irrespective of whether GRF was present, IGF-I decreased pituitary secretion of GH (P < 0.001). A significant negative response to IGF-I was already present at the dose of 50 ng mL−1 (P < 0.0001). However, the extent of the GH response to IGF-I seen in pigs of various ages differed depending on whether GRF was present. The present results therefore establish that IGF-I does exert a negative feedback on pituitary GH secretion in swine and that the age-related changes in this feedback are dependent on the presence of GRF. In swine, it appears that high circulating concentrations of GH in late-gestation fetuses are not a result of a lesser sensitivity of the somatotroph to the inhibitory actions of IGF-I. Key words: Pig, cell culture, pituitary, IGF-I, growth hormone, age

AGE-RELATED BLUNTING OF GROWTH HORMONE SECRETION IN MEN IS NOT DUE SOLELY TO INCREASED SOMATOSTATIN TONE

1998 ◽  
Vol 30 (Supplement) ◽  
pp. 106
Author(s):  
T. J. Marcell ◽  
R. A. Wiswell ◽  
S. A. Hawkins ◽  
K. T. Tarpenning
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Age Related

Gonadal and Age-Related Influences on NMDA-Induced Growth Hormone Secretion in Male Rats

1999 ◽  
Vol 69 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Leonor Pinilla ◽  
Lucas Gonzalez ◽  
Manuel Tena-Sempere ◽  
Carlos Dieguez ◽  
Enrique Aguilar
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Male Rats ◽  
Age Related

PLASMA LEVELS OF GROWTH HORMONE IN FEMALE RATS OF DIFFERENT AGES

1978 ◽  
Vol 88 (4) ◽  
pp. 676-690 ◽  
Author(s):  
Staffan Edén ◽  
Kerstin Albertsson-Wikland ◽  
Olle Isaksson
Keyword(s):  
Growth Hormone ◽  
Sequential Sampling ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Female Rats ◽  
Fasting Period ◽  
Age Related ◽  
Different Ages ◽  
Old Rats ◽  
Plasma Gh

ABSTRACT Radioimmunoassayable growth hormone (GH) was determined in fed and fasted female rats of different ages. In 6–40 day-old rats blood was collected at hourly intervals in groups of rats at different time intervals during the day. Within each age group the variation in plasma GH was considerable. In 6–14 day-old rats plasma GH was generally elevated. By day 18 levels declined, lowest on day 22 and by day 26 again increasing. In 14 day-old rats the median plasma level of GH was 22 ng/ml, in 22 day-old rats < 5 ng/ml and in 40 day-old rats 43 ng/ml. In 14 day-old rats levels ranged from < 5 ng/ml – 148 ng/ml, in 22 day-old rats from < 5 ng/ml – 34 ng/ml and in 40 day-old rats from < 5 ng/ml – > 200 ng/ml. A 20 h fasting period was associated with a significant decrease in plasma GH. In 45 day-old rats, the variations in plasma GH of individual animals were studied by obtaining sequential blood samples from unrestrained, undisturbed animals with implanted intra-aortic cannulae. In these rats GH secretion was characterized by an episodic release, occurring every 2–4 h. After a 20 h fasting period major peaks were depressed and occurred less frequently. It is concluded that there is an age-related as well as a circadian rhythm in growth hormone secretion in the rat and that sequential sampling of blood is essential for the evaluation of the secretory pattern.

Effects of repetitive administration of growth hormone-releasing hormone on growth hormone secretion, insulin-like growth factor I, and bone metabolism in postmenopausal women

1989 ◽  
Vol 120 (1) ◽  
pp. 121-128 ◽  
Author(s):  
Paul Franchimont ◽  
Didier Urbain-Choffray ◽  
Pierre Lambelin ◽  
Marie-Anne Fontaine ◽  
Gerard Frangin ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Bone Metabolism ◽  
Postmenopausal Women ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Significant Rise ◽  
Maximum Peak ◽  
Gh Secretion ◽  
Age Related ◽  
Igf I

Abstract. This study sought to determine whether GH response to synthetic GHRH was impaired in 13 postmenopausal (55-71 years) as compared with that in 8 eugonadal women and whether IGF-I and bone metabolism were consequently depressed. Thereafter, the effects of daily iv injections of 80 μg GHRH-44 for 8 days were studied in the same postmenopausal group. In addition to significantly higher basal IGF-I and osteocalcin levels (P< 0.005) in eugonadal as compared with the postmenopausal women, the administration of one GHRH-44 injection resulted in significantly higher 120-min postinjection GH maximum peak and cumulative responses in the former group as well (P< 0.005). Highly significant correlations were observed between 17β-estradiol plasma levels and either GH maximum peak or cumulative responses to GHRH-44 when both groups were pooled together, but not when considered independently. In postmenopausal women, a correlation was found between both age and duration of menopause and GH responses. Repeated GHRH-44 injections in postmenopausal women induced a significant increase in GH response (P< 0.001) as well as in IGF-I levels from day 4 to 8. No phospho-calcium parameters were modified except for a significant rise in osteocalcin from day 2 to 8. These data indicate an age-related loss of sensitivity of somatotrope cells to GHRH-44 in postmenopausal women, partly corrected by repeated daily GHRH-44 injections. As a consequence of the GHRH-induced increase in GH secretion, IGF-I was also enhanced and may be responsible for a stimulatory effect on bone formation, as shown by the osteocalcin increase, uncoupled from bone resorption.

Sign in / Sign up

Export Citation Format

Share Document