Hi Sue,
As I mentioned earlier, I don’t believe that the exact relationship between cortisol and GH has been established---it appears to be something that scientists are still trying to figure out. (See abstract belows.) The only thing that seems to be pretty certain is that excessive amounts of cortisol inhibit growth---whether it be from an inborn condition such as Cushing’s Syndrome, or from the exogenous administration of glucocorticoids. But, again, I am not sure of the mechanism by which this occurs.
The only thing that seems pretty certain is that growth is a rather complicated process that involves the interplay of a lot of different hormones and systems in the human body. Not all short children are growth hormone deficient, so it certainly isn’t as simple as just saying that the more growth hormone one secretes, the taller one is, or vice versa. There are apparently all sorts of other factors to consider like amplitude of GH waves, GH binding protein, Insulin Growth Factor I, Insulin Growth Factor II, etc., etc. What all those things are or how they all work together to translate into more height and inches, I don’t know.
From what I can tell, the abstract that you posted doesn’t make any weighty pronouncements about any of this, either. It seems to come to the basic conclusion that those taking glucocorticoids have a more regular pattern of GH secretion than those who don’t. Is that a good thing or not? I haven’t the faintest idea, and it doesn’t appear to me that these researchers make any value judgments about that, either. They only make the observation that this is the case.
In talking about dose timing, the relationship that we DO know about is the one between ACTH and cortisol. We know that increasing cortisol will make ACTH levels go down (what we want.) And we also know the approximate times that ACTH is secreted everyday (according to a circadian pattern.) If we can, then, target the amounts and times that we give cortisol, to the amounts and times that we know ACTH will rise, then---in theory---we should be able to achieve adrenal suppression, using the least amount of medication necessary (good for growth).
So, I think rearranging dose times based on circadian rhythm makes complete sense---but only because the relationship between cortisol and ACTH is known. But, since the exact relationship between cortisol and GH is not completely known, I think any assumptions that we make about what the best way is to dose in relation to GH secretion is pure conjecture, at this point.
*************************************************************
| 1: Clin Endocrinol (Oxf) 1999 Apr;50(4):473-9 | Related Articles, [unauthorised script deleted] language=JavaScript1.2>Links |
Circadian variation of plasma cortisol in prepubertal children with normal stature, short stature and growth hormone deficiency.
Hermida RC, Garcia L, Ayala DE, Fernandez JR.
Bioengineering Laboratory, ETSI Telecomunicacion, University of Vigo, Spain. rhermida@tsc.uvigo.es
OBJECTIVES: When studying the relationship between spontaneous secretion of growth hormone (GH) and cortisol in children, most studies show no correlation in mean levels of these two hormones, while others found positive or even strongly negative correlations. These contradictory results could be partly due to the inability to properly compare hormones that are characterized by circadian and ultradian variations in their secretory profiles.......... No correlation was found in circadian mean, amplitude, average, standard deviation, standard error, minimum or maximum between GH and cortisol for any of the groups of children. CONCLUSIONS: Any possible relation between GH and cortisol remains unclear. Moreover, GH-deficient children are not necessarily characterized by either hyper- or hypocortisolaemia.
PMID: 10468906 [PubMed - indexed for MEDLINE] *******************************************************************
| 1: J Clin Endocrinol Metab 1996 Feb;81(2):482-7 | Related Articles, [unauthorised script deleted] language=JavaScript1.2>Links |
Spontaneous cortisol and growth hormone secretion interactions in patients with nonclassic 21-hydroxylase deficiency (NCCAH) and control children.
Ghizzoni L, Mastorakos G, Vottero A, Magiakou MA, Chrousos GP, Bernasconi S.
Department of Pediatrics, University of Parma, Italy.
Both exogenous and endogenous hypercortisolism result in reduced GH secretion and decreased somatic growth. However, little is known about the relation between endogenous cortisol and GH secretion under physiological or slightly disturbed conditions.......
PMID: 8636254 [PubMed - indexed for MEDLINE]