axm
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Prevention of Growth Deceleration after Withdrawal of Growth Hormone Therapy in Idiopathic Short Stature
Meir Lampit, Ze’ev Hochberg. The Journal of Clinical Endocrinology & Metabolism, Volume 87, Issue 8, 1 August 2002, Pages 3573–3577. Published 01 August 2002.The treatment of children with idiopathic short stature by daily injections of human GH (hGH) is followed after its withdrawal by a growth deceleration with normal serum GH and IGF-I levels.
The present study was designed to understand and prevent growth deceleration. We hypothesized that this phenomenon is due to tolerance at the target organ level, that tolerance develops in response to the unphysiological pharmacokinetics of daily-injected hGH, and that alternate day hGH therapy will prevent it.
Thirty-eight prepubertal children with idiopathic short stature, aged 3.3–9.0 yr, were studied. Their heights were less than −2 SD score, growth rate was above the 10th percentile for age, bone age was less than 75% of chronological age, and the stimulated serum GH concentration was greater than 10 μg/liter.
The children were matched for sex, height, and growth velocity SD score to receive daily or alternate day hGH at the same weekly dose of 6 mg/m2 for a period of 2 yr. The 1st and 2nd year mean growth velocities were 3.4 and 2.3 SD score for the daily therapy group and 3.0 and 2.0 SD score for the alternate day group, respectively (P = NS).
Over the initial 6 months after withdrawal of therapy, and growth velocity decelerated to a nadir of −3.9 SD score in the daily therapy group, whereas it decelerated in the alternate day group to only −0.2 SD score (P < 0.01).
Over the entire 2 yr off therapy the latter group maintained mean growth rates of −0.2 to −1.2 SD score, similar to their pretreatment velocities. The daily group recovered slowly to resume their mean pretreatment rate only on the fourth semiannual evaluation off therapy.
The cumulative 4-yr growth velocity (2 yr on and 2 yr off therapy) of the alternate day group was greater than that of the daily therapy group (mean, 0.9 vs. 0.3 SD score; P < 0.002). At the end of the 4-yr therapy period, the adult height prediction of the alternate day group was greater than that of the daily group by a mean 6.5 cm (P = 0.06).
What does this mean?
Everyday injections of exogenous hGH seem to drastically lower your body's sensitivity to its own GH secretion.
In this study, 38 ISS children were given either everyday (ED) or every other day (EoD) injections of hGH for two years (doses equated). The treatment then ceased and their heights were tracked for an additional two years after the treatment.
During hGH therapy, both groups accelerated their growth substantially:
The ED group first and second year velocity was 3.4 and 2.3 SD.
The EoD group had 3.0 and 2.0 SD for first and second year, respectively.
Over the initial six months after withdrawal of therapy, growth velocity decelerated to a low nadir –3.9 SD score for the daily therapy group, whereas it decelerated in the alternate day group to only –0.2 SD score.
During the 2 years off therapy, the latter group taking EoD injections maintained growth rates of –0.2 to –1.2 SD score, which is similar to their SD score prior to the hGH treatment. The daily group also recovered but very slowly, on the fourth semiannual evaluation off therapy. The cumulative 4-year growth velocity—2 yrs on and 2 yrs off therapy—of the alternate day group was greater than that of the daily therapy group: mean, 0.9 vs. 0.3 SD score.
At the end of the 4-yr therapy period, the adult height prediction of the EoD group was greater than that of the daily group by a mean of 6.5 cm.
Why is this?
Typically, endogenous growth hormone comes in pulses or spikes, as opposed to a sustained release over many hours as seen in exogenous administration. It seems that the issue stems from desensitization of target tissues due to the unnatural release of growth hormone when exogenously administered subcutaneously. This is despite the fact that sustained GH release is known to boost IGF-1 higher than pulsatile secretion, further proving that GH itself contributes to growth as seen in some rodent models.
What Can We Do?
Alternate day dosing, as seen in the study, seems to ameliorate this. This is at the cost of short term height velocity though. We still do not understand how the desensitization may differ in other tissues, so it everyday dosing could maybe be considered if you believe your plates are soon to close and you want to max out height velocity during this time. Please keep in mind that the doses were equated, meaning double the dose once every other day. (as an example, from 3 IU's everyday, to 6 IU's every other day).
Another (theoretical) way this problem could be solved is through the use of peptidyl (not MK-677) growth hormone secretagogues and GHRH analogs. These peptides (especially in combination) seem to produce a spike much more similar to endogenous production. This (again, in theory) could mitigate desensitization and lead to better height gains. This is also combining with the multiple molecular weights your pituitary releases in response to the peptides as opposed to the 22 kDa exogenous hGH but that might be for a different thread.
I am not a medical professional, nothing written here should be considered medical advice. Do your own research. Thanks for reading!