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Exogenous HGH Timing: Morning or Nighttime Dosing?

In all variables we implement as bodybuilders we want to know what the “optimal” approach is. How much to do, when to do it, where to do it, etc. Human Growth Hormone dosing and timing is a variable that gets talked about a lot and a lot of times statements have little backing in scientific evidence. One of these questions is when is the best time to dose your human growth hormone (HGH)?

We can turn to the literature to help us answer these types of questions. We have several studies implementing HGH in normal health adults and children, diseased population with HIV, muscle wasting, sarcopenia, cachexia, and hypopituitarism to name a few. Dosing utilized in these studies are very “real world” as well.

Study:
“Evening Versus Morning Injections of Growth Hormone (GH) in GH-Deficient Patients: Effects on 24-Hour Patterns of Circulating Hormones and Metabolites” Jorgensen et al 1999.

Purpose:
Investigate if the timing of HGH had an impact on its action

Subjects:
Eight GH deficient (3 girls, 7 boys) mean age 14.9 +/- 1.6 years

Design:
Three 4-week study blocks in random order: 2IU GH given at 8:00am, 2IU GH given at 8:00pm, or no GH. All subjects were compared to a non-GH deficient reference range.  Serum GH, IGF-1, blood glucose, insulin, and alanine levels were monitored over 24 hours at the end of each 4-week study block.

Results:
Figure 1 below shows the change in serum GH between the AM, PM GH group, the no GH group. The shaded line is the reference group (adolescents without GH deficiency).

The 2IU AM group has a serum peak GH level of 7.3 +/-1.9 ug/L. The PM 2IU GH group had peak GH of 14.9 +/-5.8 ug/L significantly higher than the AM group.

The PM administration of GH mimicked a natural rise in nighttime GH as seen in comparison to the reference group (shaded line on figure).

AM GH administration mirrored the No GH group GH serum levels during the sleep duration with no rise in GH seen.

Serum IGF-1 was not significantly different between AM or PM dosing of HGH, 179.5 +/-5.3 ug/L and 189.8 +/-2.5 ug/L, respectively.

No difference in Serum glucose between AM and PM dosing. However, Serum insulin was significantly higher in the AM group vs the PM group.

Serum Alanine levels were higher at night in the group receiving GH in AM, I will explain the importance of this.

Conclusions:
There was an enhanced GH bioavailability with PM dosing. The authors hypothesized this could be due to elevated body temperature of subcutaneous and causing a rapid uptake of the growth hormone.

Although IGF-1 mean serum levels were not different there was a significant difference in time duration. The AM dosing had drop off at night and not achieving a steady state level like in that of the PM dosing. We want a steady state of IGF-1 as IGF-1 is the main hormone effect growth and repair.

Serum Insulin was also increased with AM dosing compared to PM dosing. AM dosing corresponds more with what we see in insulin resistance in GH administration. The PM dosing did not see this change in daytime serum insulin, as PM dosing does not have as much pancreatic beta cell challenge in a fasted state verse the fed state.

Serum Alanine levels being higher at night in the AM GH dosage are indicative of increased protein catabolism. The authors state that AM dosing of GH might be unfavorable since it induces high levels of alanine indicative of protein degradation.

Takeaway:
1.     If selecting one time of day to dose GH, pre bed may be preferable due to enhanced GH bioavailability and decreased protein catabolism compared to AM dosing.
2.     PM dosing mirrors that of normal endogenous production of GH and replacing your natural levels at a time the body is primed for GH can enhance the effects potentially.
3.     PM dosing can be favorable as well in controlling serum insulin levels and decreasing stress on beta cell function.