Testosterone supplementation, Older Men, GH IGF-1, Arganine GHRH GHRP-2

[O-Train]

I was curious about GHRH and GHRP so I started searching PubMed. Was going to post this article in the Article section but it doesn't get enough traffic. It's an interesting article. I'll post up more here if I find any.

http://eje-online.org/cgi/reprint/153/4/577 (Free full text)

Abstract

Testosterone supplementation in healthy older men drives GH and IGF-I secretion without potentiating peptidyl secretagogue efficacy.
Veldhuis JD, Keenan DM, Mielke K, Miles JM, Bowers CY.
Department of Internal Medicine, Mayo Medical and Graduate Schools of Medicine, General Clinical Research Center, Mayo Clinic, Rochester, MN 55905, USA. veldhuis.johannes@mayo.edu

OBJECTIVE: Testosterone supplementation increases GH and IGF-I concentrations in healthy older men via unknown mechanisms. We examine the hypotheses that (i) testosterone amplifies stimulation of GH secretion by GH-releasing peptide (GHRP)-2 or GH-releasing hormone (GHRH) infused with l-arginine to limit somatostatin outflow (i.e. upregulates each agonistic pathway), (ii) testosterone augments the effect of both peptidyl secretagogues infused together (i.e. reduces opposition by hypothalamic somatostatin) and (iii) abdominal visceral fat (AVF) mass is a negative determinant of specific secretagogue-stimulated GH secretion. DESIGN: Randomized double-blind crossover design of placebo versus testosterone administration in healthy older men. METHODS: Deconvolution analysis was used to estimate basal GH secretion and the mass (integral) and waveform (time-shape) of GH secretory bursts. RESULTS: Statistical contrasts revealed that administration of testosterone compared with placebo in seven men aged 60-77 years increased fasting concentrations of GH (P < 0.01) and IGF-I (P = 0.003), and basal (P < 0.005) and pulsatile (P < 0.01) GH secretion. Testosterone did not alter the absolute value or rank order of secretagogue efficacy: l-arginine/GHRP-2 (23-fold effect over saline) = GHRH/GHRP-2 (20-fold) > l-arginine/GHRH (7.5-fold). Waveform reconstruction indicated that each stimulus pair accelerated initial GH secretion within a burst (P < 0.01). Regression analysis disclosed a significant inverse association between GH secretory-burst mass and computer tomography-estimated AVF following stimulation with l-arginine/GHRH after testosterone supplementation (R(2) = 0.54, P = 0.015). CONCLUSION: Supraphysiological testosterone concentrations augment GH and IGF-I production in the elderly male without altering maximal somatotrope responses to single and combined GHRH and GHRP-2 drive, thus predicting multifactorial mechanisms of testosterone upregulation.

[O-Train]

This is also an interesting article looking at GHRP-2 and GHRH administration. Focuses primarily on elderly men and women but also young men and women.

http://jcem.endojournals.org/cgi/reprint/89/5/2290 (Free Full Text)

Abstract

Sustained elevation of pulsatile growth hormone (GH) secretion and insulin-like growth factor I (IGF-I), IGF-binding protein-3 (IGFBP-3), and IGFBP-5 concentrations during 30-day continuous subcutaneous infusion of GH-releasing peptide-2 in older men and women.
Bowers CY, Granda R, Mohan S, Kuipers J, Baylink D, Veldhuis JD.
Tulane University Health Sciences Center, New Orleans, Louisiana 70112, USA. rjabowers@tulane.edu

We test the interlinked hypotheses that in healthy older adults: 1). i.v. injection of GH-releasing peptide-2 (GHRP-2) and GHRH synergizes more in aging women than men; 2). sc infusion of both GHRP-2 (1 microg/kg.h = 1) and GHRH (1, 3, or 10) for 24 h augments GH secretion more than either agonist alone; and 3). continuous sc delivery of GHRP-2 (1) for 30 d stimulates daily GH secretion and IGF-I, IGF-binding protein-3 (IGFBP-3), and IGFBP-5. Acute two-peptide synergy was 3-fold greater in young (n = 16) than older volunteers (n = 17; P < 0.025) and was 2.3-fold higher in elderly women than men (P < 0.025). The 24-h infusion of GHRP-2 (1) combined with GHRH (3 or 10) in men and with GHRH (10) in women drove GH secretion more than GHRH alone (P <or= 0.024). In the entire cohort (n = 11), GHRP-2/GHRH (1/10) stimulated GH secretion more than either GHRP-2 (1; P = 0.021) or GHRH (10; P = 0.012). The 30-d delivery of GHRP-2 (1; n = 17 subjects): 1). stimulated pulsatile, rhythmic, and entropic GH secretion by more than 3-fold on d 1 and more than 1.8-fold on d 14 and 30 (each P < 0.001 vs. saline); 2). elevated IGF-I to a stable plateau on d 1, 14, and 30 (P < 0.025 vs. baseline); and 3). increased IGFBP-3 (P < 0.01) and IGFBP-5 (P < 0.025) on d 14 and/or 30. Safety screening tests remained normal. In summary, in healthy elderly women and men: 1). acute synergy of GHRP-2 and GHRH is greater in the female; 2). 24-h combined GHRP-2 and GHRH drive is more effective than either agonist alone; and 3). 30-d stimulation with GHRP-2 sustains a physiologically activated somatotropic axis. We conclude that age, gender, stimulus duration, and secretagogue combination determine acute, intermediate, and extended responses of the somatotropic axis in the older adult.

[O-Train]

Just as a sidenote, something I read about that I'm sure a lot of people already know. Obesity greatly reduces the secretion of Growth Hormone.

[O-Train]

This is also kind of an interesting article. Looks at the reduction of free fatty acids enhancing the GH response caused by administration of GHRP-2.

http://jcem.endojournals.org/cgi/reprint/85/12/4706 (Free Full Text)

Abstract

Reduction of free fatty acids by acipimox enhances the growth hormone (GH) responses to GH-releasing peptide 2 in elderly men.
Van Dam PS, Smid HE, de Vries WR, Niesink M, Bolscher E, Waasdorp EJ, Dieguez C, Casanueva FF, Koppeschaar HP.
Departments of Clinical Endocrinology, University Medical Center, 3508 GA Utrecht, The Netherlands. P.S.vanDam@digd.azu.nl

GH release is increased by reducing circulating free fatty acids (FFAs). Aging is associated with decreased plasma GH concentrations. We evaluated GH releasing capacity in nine healthy elderly men after administration of GH-releasing peptide 2 (GHRP-2), with or without pretreatment with the antilipolytic drug acipimox, and compared the GHRP-2-induced GH release with the response to GHRH. The area under the curve (AUC) of the GH response after GHRP-2 alone was 4.8 times higher compared with GHRH alone (1834 +/- 255 vs. 382 +/- 78 microg/L.60 min, P: < 0.001). Acipimox, which reduced FFAs from 607 micromol/L to 180 micromol/L, increased the GH AUC to 1087 after GHRH and to 2956 microg/L.60 min after GHRP-2 (P: < 0.01). The AUC after acipimox/GHRP-2 were positively correlated with the AUC after GHRP-2 alone (r = 0.93, P: < 0.01); this was also observed between acipimox/GHRH and GHRH alone (r = 0.73, P: = 0.03). Significant negative correlations were observed between basal FFAs and AUC after GHRH or GHRP-2 after combining the data with and without acipimox (r = 0.58, P: = 0.01 and r = 0.48, P: = 0.04, respectively), and between basal FFAs and GH at t = 0 (r = -0.44, P: = 0.001). Interestingly, GHRP-2 administration was followed by a significant early rise in plasma FFAs by 60% (P = 0.01), indicating an acute lipolytic effect. In conclusion, reduction of circulating FFAs strongly enhances GHRP-2-stimulated GH release in elderly men. The data indicate that the decreased GH release associated with aging can be reversed by acipimox and that the pituitary GH secretory capacity in elderly men is still sufficient.

I found this part of the Discussion particularly interesting:

While the present data show that reduction of FFAs increases
GH release, we could also demonstrate a significant
rise in circulating FFAs within 30 min after GHRP-2 administration.
This acute rise might be the consequence of an acute
lipolytic effect of GHRP-2 or another GHRP-2-mediated effect.
Previous studies have shown that after sc administration
of GH, lipolysis and rise of FFAs occurs after 120 min (29).
Taking into account that GHRP receptors are expressed in
adipose tissue (30), it is possible that the rapid increase in
plasma FFAs after GHRP-2 administration is exerted by a
direct effect of this peptide on the adipocytes. Furthermore,
it cannot be ruled out that other mechanisms such as GHRP-
2-induced co-release of other pituitary hormones such as
ACTH or TSH could be responsible for the rapid increase in
plasma FFAs after GHRP-2 administration.
In conclusion, the present data demonstrate that GHRP-
2-stimulated GH secretion in the elderly can be enhanced by
the reduction of circulating FFAs and that, under these circumstances,
GHRP-2-mediated GH release is strongly increased
in comparison with the effect of GHRH. Furthermore,
administration of GHRP-2 induces an acute lipolytic
effect. The exact contribution of changes in FFAs to the agerelated
decline in GH secretion remains to be determined,
given the large number of hormonal and metabolic changes
associated with aging. Our data show that the pituitary GH
secretory capacity in elderly men is still intact, and that the
attenuated GH secretion in this population can be overcome
by the reduction of FFA.

[O-Train]

This article discusses a growth hormone secretagogue called Ipamorelin. Hadn't heard of it before.

http://eje-online.org/cgi/reprint/139/5/552 (Free Full Text)

Abstract

Ipamorelin, the first selective growth hormone secretagogue.
Raun K, Hansen BS, Johansen NL, Thøgersen H, Madsen K, Ankersen M, Andersen PH.
Department of GH Biology, Novo Nordisk A/S, Måløv, Denmark.

The development and pharmacology of a new potent growth hormone (GH) secretagogue, ipamorelin, is described. Ipamorelin is a pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2), which displays high GH releasing potency and efficacy in vitro and in vivo. As an outcome of a major chemistry programme, ipamorelin was identified within a series of compounds lacking the central dipeptide Ala-Trp of growth hormone-releasing peptide (GHRP)-1. In vitro, ipamorelin released GH from primary rat pituitary cells with a potency and efficacy similar to GHRP-6 (ECs) = 1.3+/-0.4nmol/l and Emax = 85+/-5% vs 2.2+/-0.3nmol/l and 100%). A pharmacological profiling using GHRP and growth hormone-releasing hormone (GHRH) antagonists clearly demonstrated that ipamorelin, like GHRP-6, stimulates GH release via a GHRP-like receptor. In pentobarbital anaesthetised rats, ipamorelin released GH with a potency and efficacy comparable to GHRP-6 (ED50 = 80+/-42nmol/kg and Emax = 1545+/-250ng GH/ml vs 115+/-36nmol/kg and 1167+/-120ng GH/ml). In conscious swine, ipamorelin released GH with an ED50 = 2.3+/-0.03 nmol/kg and an Emax = 65+/-0.2 ng GH/ml plasma. Again, this was very similar to GHRP-6 (ED50 = 3.9+/-1.4 nmol/kg and Emax = 74+/-7ng GH/ml plasma). GHRP-2 displayed higher potency but lower efficacy (ED50 = 0.6 nmol/kg and Emax = 56+/-6 ng GH/ml plasma). The specificity for GH release was studied in swine. None of the GH secretagogues tested affected FSH, LH, PRL or TSH plasma levels. Administration of both GHRP-6 and GHRP-2 resulted in increased plasma levels of ACTH and cortisol. Very surprisingly, ipamorelin did not release ACTH or cortisol in levels significantly different from those observed following GHRH stimulation. This lack of effect on ACTH and cortisol plasma levels was evident even at doses more than 200-fold higher than the ED50 for GH release. In conclusion, ipamorelin is the first GHRP-receptor agonist with a selectivity for GH release similar to that displayed by GHRH. The specificity of ipamorelin makes this compound a very interesting candidate for future clinical development.

[O-Train]

This article looks at the combined administration of GHRH and GHRP-6 on people of different ages. Apparently the combination of GHRH and GHRP-6 is considered the most potent stimulus of GH secretion. I'm not sure if that's changed since the article was published in 1998.

http://jcem.endojournals.org/cgi/reprint/83/7/2569 (Free Full Text)

Abstract

Preserved growth hormone (GH) secretion in aged and very old subjects after testing with the combined stimulus GH-releasing hormone plus GH-releasing hexapeptide-6.
Micic D, Popovic V, Doknic M, Macut D, Dieguez C, Casanueva FF.
Institute of Endocrinology, University Clinical Centre, Belgrade, Yugoslavia.

Either spontaneous or pharmacological stimulated GH secretion is reduced with advanced age. This observation is an added difficulty for the biochemical diagnosis of GH deficiency in adults. Furthermore, the combined administration of saturating doses of GH-releasing hormone (GHRH) plus GH-releasing hexapeptide (GHRP)-6 is nowadays the most effective GH-releasing stimulus tested in a variety of settings related to altered somatotroph function. To understand whether the GH discharge elicited by the combined stimulus declines with age, 26 normal subjects of both sexes, divided into 3 age groups [adults 19-40 yr; aged 46-65 yr; and very old (75-96 yr) subjects] were studied. They were administered i.v., as bolus and in combination, 90 micrograms GHRH plus 90 micrograms GHRP-6. In the three groups, the combined administration of GHRH plus GHRP-6 elicited a GH area under the curve (microgram/L per 120 min) of 3,127 +/- 262, 3,409 +/- 573, and 4,655 +/- 737 for adults, aged, and very old subjects, respectively (nonsignificant differences). The mean GH peak was 47.5 +/- 4.5 micrograms/L for adults, 52.9 +/- 8.4 micrograms/L for aged subjects, and 76.0 +/- 11.7 for very old subjects (nonsignificant differences). Individually examined, there were no nonresponders to the combined stimulus, and all subjects (independently of age) showed a GH peak over 25 micrograms/L (the lowest peak was 27.3 micrograms/L, and the highest peak was 119.2 micrograms/L). In conclusion, the GHRH plus GHRP-6-induced GH release is well preserved in aged and very old subjects, which suggests that the GH secretory capability of the combined test is not reduced by age. This combined test may be useful for the diagnosis of GH-deficient states in adults.

[O-Train]

This article looks at administration of CJC-1295. Basically GHRH but with a much longer half life (8 days).

http://jcem.endojournals.org/cgi/reprint/91/12/4792 (Free Full Text)

Abstract

Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analog.
Ionescu M, Frohman LA.
Section of Endocrinology, Metabolism, and Diabetes, University of Illinois at Chicago, 1747 West Roosevelt Road, Room 517, Chicago, Illinois 60608, USA.

CONTEXT: Pulsatile GH secretion is considered important for many of the hormone's physiological effects. Short-term GHRH infusions enhance GH pulsatility and increase IGF-I, but the short GHRH half-life limits its therapeutic use. A synthetic GHRH analog (CJC-1295) that binds permanently to endogenous albumin after injection (half-life = 8 d) stimulates GH and IGF-I secretion in several animal species and in normal human subjects and enhances growth in rats. OBJECTIVE: Our objective was to assess GH pulsatility after a single injection of CJC-1295 and determine which GH secretion parameters correlated to the increase in IGF-I production. METHODS: GH pulsatility was assessed by 20-min blood sampling during an overnight 12-h period in healthy 20- to 40-yr-old men before and 1 wk after injection of either 60 or 90 microg/kg CJC-1295. RESULTS: GH secretion was increased after CJC-1295 administration with preserved pulsatility. The frequency and magnitude of GH secretory pulses were unaltered. However, basal (trough) GH levels were markedly increased (7.5-fold; P < 0.0001) and contributed to an overall increase in GH secretion (mean GH levels, 46%; P < 0.01) and IGF-I levels (45%; P < 0.001). No significant differences were observed between the responses to the two drug doses. The IGF-I increases did not correlate with any parameters of GH secretion. CONCLUSIONS: CJC-1295 increased trough and mean GH secretion and IGF-I production with preserved GH pulsatility. The marked enhancement of trough GH levels by continuous GHRH stimulation implicates the importance of this effect on increasing IGF-I. Long-acting GHRH preparations may have clinical utility in patients with intact pituitary GH secretory capability.

[O-Train]

This article is very interesting. Looks at CJC-1295 administration in healthy adults. It appears to be safe and well tolerated at doses of 30 or 60 micrograms/kg. This study reported an estimated half-life of 5.8-8.1 days.

http://jcem.endojournals.org/cgi/reprint/91/3/799 (Free Full Text)

Abstract

Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults.
Teichman SL, Neale A, Lawrence B, Gagnon C, Castaigne JP, Frohman LA.
WinPharm Associates, Alamo, CA 94507, USA.

CONTEXT: Therapeutic use of GHRH to enhance GH secretion is limited by its short duration of action. OBJECTIVE: The objective of this study was to examine the pharmacokinetic profile, pharmacodynamic effects, and safety of CJC-1295, a long-acting GHRH analog. DESIGN: The study design was two randomized, placebo-controlled, double-blind, ascending dose trials with durations of 28 and 49 d. SETTING: The study was performed at two investigational sites. PARTICIPANTS: Healthy subjects, ages 21-61 yr, were studied. INTERVENTIONS: CJC-1295 or placebo was administered sc in one of four ascending single doses in the first study and in two or three weekly or biweekly doses in the second study. MAIN OUTCOME MEASURES: The main outcome measures were peak concentrations and area under the curve of GH and IGF-I; standard pharmacokinetic parameters were used for CJC-1295. RESULTS: After a single injection of CJC-1295, there were dose-dependent increases in mean plasma GH concentrations by 2- to 10-fold for 6 d or more and in mean plasma IGF-I concentrations by 1.5- to 3-fold for 9-11 d. The estimated half-life of CJC-1295 was 5.8-8.1 d. After multiple CJC-1295 doses, mean IGF-I levels remained above baseline for up to 28 d. No serious adverse reactions were reported. CONCLUSIONS: Subcutaneous administration of CJC-1295 resulted in sustained, dose-dependent increases in GH and IGF-I levels in healthy adults and was safe and relatively well tolerated, particularly at doses of 30 or 60 microg/kg. There was evidence of a cumulative effect after multiple doses. These data support the potential utility of CJC-1295 as a therapeutic agent.

[O-Train]

Another article regarding CJC-1295. This one goes into how CJC-1295 was identified, along with the two other compounds (CJC-1288 and CJC-1293) that were all derived from GRF1-29.

Just to clarify (as I understand it) GHRH is a 44 amino acid peptide also known as GRF or GHRF (Growth Hormone Releasing Factor) or Somatocrinin. It gave rise to a 29 amino acid peptide which most people know as GRF1-29 or Sermorelin. GRF1-29 gave rise to CJC-1295 which has a much longer half-life.

http://endo.endojournals.org/cgi/reprint/146/7/3052 (Free Full Text)

Abstract

Human growth hormone-releasing factor (hGRF)1-29-albumin bioconjugates activate the GRF receptor on the anterior pituitary in rats: identification of CJC-1295 as a long-lasting GRF analog.
Jetté L, Léger R, Thibaudeau K, Benquet C, Robitaille M, Pellerin I, Paradis V, van Wyk P, Pham K, Bridon DP.
Department of Research, ConjuChem Inc., 225 President-Kennedy Avenue, Montreal, Quebec, Canada H2X 3Y8.

In vivo bioconjugation to the free thiol on Cys34 of serum albumin by a strategically placed reactive group on a bioactive peptide is a useful tool to extend plasma half-life. Three maleimido derivates of human GH-releasing factor (hGRF)(1-29) were synthesized and bioconjugated to human serum albumin ex vivo. All three human serum albumin conjugates showed enhanced in vitro stability against dipeptidylpeptidase-IV and were bioactive in a GH secretion assay in cultured rat anterior pituitary cells. When the maleimido derivatives were individually administered sc to normal male Sprague Dawley rats, an acute secretion of GH was measured in plasma. The best compound, CJC-1295, showed a 4-fold increase in GH area under the curve over a 2-h period compared with hGRF(1-29). CJC-1295, a tetrasubstituted form of hGRF(1-29) with an added N epsilon-3-maleimidopropionamide derivative of lysine at the C terminus, was selected for further pharmacokinetic evaluation, where it was found to be present in plasma beyond 72 h. A Western blot analysis of the plasma of a rat injected with CJC-1295 showed the presence of a CJC-1295 immunoreactive species on the band corresponding to serum albumin, appearing after 15 min and remaining in circulation beyond 24 h. These results led to the identification of CJC-1295 as a stable and active hGRF(1-29) analog with an extended plasma half-life.

[rufusrocks]

This article looks at administration of CJC-1295. Basically GHRH but with a much longer half life (8 days).

http://jcem.endojournals.org/cgi/reprint/91/12/4792 (Free Full Text)

Abstract

Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analog.
Ionescu M, Frohman LA.
Section of Endocrinology, Metabolism, and Diabetes, University of Illinois at Chicago, 1747 West Roosevelt Road, Room 517, Chicago, Illinois 60608, USA.

CONTEXT: Pulsatile GH secretion is considered important for many of the hormone's physiological effects. Short-term GHRH infusions enhance GH pulsatility and increase IGF-I, but the short GHRH half-life limits its therapeutic use. A synthetic GHRH analog (CJC-1295) that binds permanently to endogenous albumin after injection (half-life = 8 d) stimulates GH and IGF-I secretion in several animal species and in normal human subjects and enhances growth in rats. OBJECTIVE: Our objective was to assess GH pulsatility after a single injection of CJC-1295 and determine which GH secretion parameters correlated to the increase in IGF-I production. METHODS: GH pulsatility was assessed by 20-min blood sampling during an overnight 12-h period in healthy 20- to 40-yr-old men before and 1 wk after injection of either 60 or 90 microg/kg CJC-1295. RESULTS: GH secretion was increased after CJC-1295 administration with preserved pulsatility. The frequency and magnitude of GH secretory pulses were unaltered. However, basal (trough) GH levels were markedly increased (7.5-fold; P < 0.0001) and contributed to an overall increase in GH secretion (mean GH levels, 46%; P < 0.01) and IGF-I levels (45%; P < 0.001). No significant differences were observed between the responses to the two drug doses. The IGF-I increases did not correlate with any parameters of GH secretion. CONCLUSIONS: CJC-1295 increased trough and mean GH secretion and IGF-I production with preserved GH pulsatility. The marked enhancement of trough GH levels by continuous GHRH stimulation implicates the importance of this effect on increasing IGF-I. Long-acting GHRH preparations may have clinical utility in patients with intact pituitary GH secretory capability.

i saw a WIKI article on CJC 1295 they were doing a study on AIDS patients with this but 3 people died of heart failure so the study was stopped.

[O-Train]

i saw a WIKI article on CJC 1295 they were doing a study on AIDS patients with this but 3 people died of heart failure so the study was stopped.

From the articles I read regarding healthy people I didn't notice any adverse health conditions. Although some of these peptides have not been extensively studied and are probably not fully understood.

The sticky on CJC-1295 and GHRP-6 indicates that these two peptides taken in combination produce the most results. That confirms what I've read. The only missing piece I think is control of Somatostatin. One article I read mentioned using L-arginine infusion before peptide administration to decrease the effects of Somatostatin. I'm not sure this would be practical, are there other approaches that people know of and/or have tried? I wonder if taking a large dose of l-arginine orally would produce any significant effect? I guess that would basically be a NO supplement.

I kind of wonder what the potential risks are when you self regulate these powerful hormones. The obvious problem is that hormones have so many different actions in the body. So you could be taking something for one reason and only considering that one aspect but so many other things are also being effected.

[zziggzzigg]

interesting studies o hurley

what is your conclusion for guys that are getting older? I'm wondering about using hgh instead of test and letting natural test recover and hoping the hgh helps the pituitary produce more lh for a better natural test level?

[O-Train]

interesting studies o hurley

what is your conclusion for guys that are getting older? I'm wondering about using hgh instead of test and letting natural test recover and hoping the hgh helps the pituitary produce more lh for a better natural test level?

I found an excerpt from a book online titled: Androgens in health and disease. Won't let me copy and paste so I'll type it out.

Growth hormone (GH) has been proposed to stimulate testosterone biosynthesis directly, or via testicular insulin-like growth factor-1 (IGF-1) and IGF-1 receptors on Leydig cells. In rodents, testicular IGF-1 is upregulated by gonadotropins and may play a role in the differentiation of immature into adult Leydig cells. In IGF-1 deficient mice, testosterone levels are 18% of normal, although this may be the result of gonadotropin deficiency. The testes are smaller than normal in men with childhood-onset GH deficiency; however, circulating testosterone levels are generally normal. In adult men with isolated GH deficiency as a result of hypothalmic-pituitary disease, plasma testosterone levels increased slightly following 6-12 mo of human GH (hGH) therapy, and the testosterone response to hCG stimulation was increased by 20%. Thus, GH may play a minor role in testosterone production. There is a direct stimulatory effect of T3 on the production of testosterone and estradiol by Leydig cells, in part by increasing StAR expression.

Cole's Notes version is that it may help your test levels although this may only happen if you have lower than normal GH levels. Which is a normal result of the aging process. I can't say for certainty but I would think that GH wouldn't have close to the same effect on test levels when compared to a reasonable HRT dosage. Not to say that GH doesn't have many other effects and/or benefits.