Will IGF-1 increase substantially by increasing the dose from 12.5 mg to 25 mg or even up to 50mg? Here is a very good study that investigated just that:
an M. Chapman, Ora H. Pescovitz, Gail Murphy, Theresa Treep, Kristine A. Cerchio, David Krupa, Barry Gertz, William J. Polvino, Emily H. Skiles, Suzan S. Pezzoli, Michael O. Thorner, Oral Administration of Growth Hormone (GH) Releasing Peptide-Mimetic MK-677 Stimulates the GH/Insulin-Like Growth Factor-I Axis in Selected GH-Deficient Adults,
The Journal of Clinical Endocrinology & Metabolism, Volume 82, Issue 10, 1 October 1997, Pages 3455–3463,
Oral Administration of Growth Hormone (GH) Releasing Peptide-Mimetic MK-677 Stimulates the GH/Insulin-Like Growth Factor-I Axis in Selected GH-Deficient Adults*
Serum IGF-I and 24-h mean GH concentrations increased in all subjects after treatment with both 10 and 50 mg/day MK-677
vs. baseline. After treatment with 10 mg MK-677, IGF-I concentrations increased 52 ± 20% (65± 6 to 99 ± 9 μg/L, geometric mean ± intrasubject SE,
P ≤ 0.05
vs. baseline), and 24 h mean GH concentrations increased 79 ± 19% (0.14 ± 0.01 to 0.26 ± 0.02 μg/L,
P ≤ 0.05
vs. baseline). Following treatment with 50 mg MK-677, IGF-I concentrations increased 79 ± 9% (84 ± 3 to 150 ± 6 μg/L,
P ≤ 0.05
vs. baseline) and 24-h mean GH concentrations increased 82 ± 29% (0.21 ± 0.02 to 0.39 ± 0.04μ g/L,
P ≤ 0.05
vs. baseline), respectively. Serum IGF binding protein-3 concentrations increased with both 10 mg (1.2 ± 0.1 to 1.7 ± 0.1 μg/L,
P ≤ 0.05) and 50 mg MK-677 (1.7 ± 0.1 to 2.2 ± 0.2 μg/L,
P ≤ 0.05). The GH response to MK-677 was greater in subjects who were the least GH/IGF-I deficient at baseline; by linear regression analysis the increase in 24-h mean GH concentration was positively related to both baseline 24-h mean GH concentration (r = 0.81,
P = 0.009) and baseline IGF-I (r = 0.79,
P = 0.01) for 10 mg MK-677. IGF-I responses were not significantly related to any baseline measurement. Fasting and postprandial insulin and postprandial glucose increased significantly after MK-677 treatment, and the clinical significance of these changes will need to be assessed in longer term studies. Oral administration of such GHRP-mimetic compounds may have a role in the treatment of GH deficiency of childhood onset.
So with 10mg. GH increased about 79%, IGF-1 increased about 52%
50mg GH increased 82% and IGF-1 increased about 79%
IGFBP-3 was also greatly increased over baseline. IGFBP-3 is the main carrier of somatomedin C (also called insulin-like growth factor-1, or IGF-1) in the body.
MK-677 treatment was generally well tolerated and no symptoms developed that were definitely attributed to study drug. There were no serious adverse events during this study, and no subjects were discontinued or had treatment interrupted because of an adverse experience.
Something to consider: IGF-I and GH concentrations were significantly increased after 2 weeks treatment with oral MK-677 in healthy older subjects. Moreover, IGF-I concentrations increased further between 2–4 weeks of treatment, indicating that the full effect of MK-677 on IGF-I concentrations took longer than 2 weeks to develop, and that significant stimulation of the GH/IGF-I axis was sustained for at least a month
