The Effect of Androgens on the Pulsatile Release and the Twenty-Four-Hour Mean Concentration of Growth Hormone in Peripubertal Males*

Link, Kathleen; Blizzard, Robert M.; Evans, William S.; Kaiser, Donald L.; Parker, Mark W.; Rogol, Alan D.

doi:10.1210/jcem-62-1-159

Cited by 192 publications

(85 citation statements)

References 28 publications

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“…[29][30][31] The rise of GH and IGF1 is stimulated at puberty by an increase of gonadal and adrenal sex hormones. [32][33][34][35] The close inverse relationship between physical fitness and HR has been demonstrated in previous experimental 36,37 and epidemiological studies 38,39 at any age and in both sexes. Physical activity can be regarded as a useful and physiological method for decreasing HR, and its cardioprotective action could be partially explained through the effects on HR.…”

Section: Discussionmentioning

confidence: 95%

Assessing resting heart rate in adolescents: determinants and correlates

et al. 2002

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The aim of this study was to evaluate the distribution of resting heart rate and its biological and environmental determinants in adolescents. The study was crosssectional and the population consisted of 2230 children and adolescents, age range 12-18 years, enrolled randomly from state schools in Turin, Italy. In all participants the following parameters were evaluated: heart rate, blood pressure (BP), weight, height, degree of sexual development, physical activity, parental socio-cultural level. Heart rate and BP were measured after 5, 10 and 15 min in a sitting position. Furthermore, to obtain regression equations to define heart rate as a function of the other variables available, a multiple regression analysis was performed. In both sexes BP, but not heart rate, declined significantly from the first to the last

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Section: Discussionmentioning

confidence: 95%

Assessing resting heart rate in adolescents: determinants and correlates

et al. 2002

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“…This hypothesis is further supported by the present findings that in spite of sex difference in the secretion profile of GH in Landrace pigs (Arbona et al 1988), there was no sex difference in the constitutive expression of hepatic CYP1A subfamily enzymes. On the other hand, the modification of the secretion profile of GH by androgen administration had been reported (Davis et al 1977, Somana et al 1978, Link et al 1986, Dubreuil et al 1989. Accordingly, drastic decreases in the levels of CYP1A subfamily enzymes in androgen-treated Landrace pigs might occur, at least in part, through the change in secretion profile of GH, especially the emphasis of a male-type secretion profile.…”

Section: Discussionmentioning

confidence: 99%

Androgen-mediated down-regulation of CYP1A subfamily genes in the pig liver

Kojima¹,

Sekimoto²,

Degawa³

2010

Journal of Endocrinology

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In Meishan and Landrace pigs, sex differences in the constitutive expression of hepatic cytochrome P4501A (CYP1A) subfamily enzymes were examined in terms of their mRNA, protein, and enzyme activity. All the results from the real-time RT-PCR, western blotting, and enzyme assays for CYP1A subfamily enzymes indicated that, in 5-month-old Meishan pigs, the expression levels of CYP1A1 and CYP1A2 in males were significantly low as compared with those in females. In contrast, there were no such significant sex differences in Landrace pigs. Castration of male Meishan pigs led to a female-type expression of the CYP1A subfamily enzymes, whereas no such effect was observed in male Landrace pigs after castration. In both breeds of pigs, the administration of testosterone propionate to the females and castrated males led to marked decreases in the expression levels of mRNAs and proteins in the CYP1A subfamily enzymes, and also in their enzyme activities. Furthermore, the correlation analyses between the serum testosterone level and the gene expression levels of CYP1A subfamily enzymes in different sex-matured (1-5-month-old) male pigs revealed that the clear decrease in expression levels of hepatic CYP1A subfamily enzymes occurred at concentrations of more than 33 ng/ml of serum testosterone. Incidentally, the mean concentrations of serum testosterone in 5-month-old Landrace and Meishan pigs were around 18 and 50 ng/ml respectively. In conclusion, we demonstrated for the first time that the serum testosterone level is one of the physiological factors which regulate constitutive expression of hepatic CYP1A1 and CYP1A2 in pigs.

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“…The increase in IGF-I is due to GH rather than direct effects of testosterone, since IGF-I is increased by co-administration of GH and testosterone but not by testosterone alone in GH-deficient boys (Parker et al 1984). The influence of testosterone on GH secretion is also illustrated by the ability of exogenous testosterone to correct deficient basal and GHRH-stimulated GH secretion in boys with gonadal dysfunction (Link et al 1986, Mauras et al 1989a. Androgens induce GH secretion via aromatization to estrogens, since non-aromatizable forms of testosterone, such as dihydrotestosterone (DHT), inhibit (Keenan et al 1993) or have no effect , Eakman et al 1996 on GH secretion in pubertal boys.…”

Section: Puberty: Humansmentioning

confidence: 99%

GH as a co-gonadotropin: the relevance of correlative changes in GH secretion and reproductive state

Hull

Harvey

2002

Journal of Endocrinology

104

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It is now well established that exogenous GH promotes sexual maturation and reproductive function. The possibility that this may reflect physiological actions of endogenous GH has, however, rarely been considered. Correlative changes in GH secretion and reproductive state (puberty, pregnancy, lactation, menopause and ovarian cycles) are thus the primary focus of this review. GH secretion is, for instance, elevated during major transitions in reproductive status such as puberty and pregnancy. In some cases, augmented circulating GH levels are paired with hepatic GH resistance. This interaction may permit selective activation of gonadal responses to GH without activating IGF-I-mediated systemic responses. This selective activation may also be mediated by autocrine, paracrine or intracrine GH actions, since GH is also synthesized in reproductive tissues. Correlative changes in GH secretion and reproductive state may be mediated by events at the hypothalamic, pituitary and gonadal level. In addition to direct effects on gonadal function, GH may influence reproductive activity by increasing gonadotropin secretion at the hypothalamic and pituitary level and by enhancing gonadotropin responsiveness at the gonadal level. The close association between reproductive status and the somatotrophic axis supports the physiological importance of GH in reproductive function.

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The Effect of Androgens on the Pulsatile Release and the Twenty-Four-Hour Mean Concentration of Growth Hormone in Peripubertal Males*

Cited by 192 publications

References 28 publications

Assessing resting heart rate in adolescents: determinants and correlates

Assessing resting heart rate in adolescents: determinants and correlates

Androgen-mediated down-regulation of CYP1A subfamily genes in the pig liver

GH as a co-gonadotropin: the relevance of correlative changes in GH secretion and reproductive state

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