GH and aging

[Guest guest]

Hi All,

Two interesting GH related papers:

http://www.lef.org/magazine/mag2002/mar2002_medup.html

It should be noted that the level of insulin also effects the level of IGF-1 and

low GH in aged folks is normally

associated with elevated fatty acid and glucose levels in the blood.

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GH replacement therapy and VLDL cholesterol

Those with adult GH deficiency are often dyslipidemic and may have an increased

risk of cardiovascular disease. The

secretion and clearance of very low density Lipoprotein (VLDL) are important

causes of blood lipid (fat) concentrations.

This study examined the effect of GH replacement therapy on VLDL metabolism.

VLDL kinetics was determined in 14 adult

patients with GH deficiency before and after 3 months GH or placebo treatment.

GH replacement therapy increased blood

insulin-like growth factor I (IGF-1) concentrations 2.9-fold, fasting insulin

concentrations 1.8-fold, and hemoglobin

A(1C) from 5.0% to 5.3%. It decreased fat mass by 3.4 kg and increased lean body

mass by 3.5 kg. The total cholesterol

concentration, the low-density lipoprotein (LDL) cholesterol concentration, and

the VLDL cholesterol/VLDL ratio

decreased. GH therapy did not significantly change the VLDL pool size, but

increased the VLDL secretion rate from 9.2 to

25.9 mg/kg day and the MCR from 11.5 to 20.3 ml/min. No significant changes were

observed in the placebo group.

This study suggests that GH replacement therapy improves lipid profile by

increasing the removal of VLDL.

Although GH therapy actually stimulates VLDL secretion, this increase in VLDL is

ultimately reduced by the increase in

the VLDL clearance rate, which the researchers postulate is due to its effects

in increasing low density lipoprotein

(LDL) receptors and modifying VLDL composition.

JOURNAL OF CLINICAL ENDOCRINOLOGY AND METABOLISM, 1999, Vol 84, Iss 1, pp

307-316

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The IGF-I response to very low GH doses in human aging

The activity of the growth hormone(GH)/IGF-I axis varies during life and is

reduced in the elderly. In fact, GH, and

IGF-I levels in older people are similar to those observed in patients with GH

deficiency. The declining activity of the

GH/IGF-I axis with advancing age may contribute to changes in body composition,

structure, function and metabolism. In

fact, treatment with pharmacological doses of GH restored plasma IGF-I levels,

increased lean body mass and muscle

strength while decreased adipose (fat) tissue mass in healthy elderly subjects.

This study aimed to verify the effect of both single dose (Group 1: 20 mu g/kg)

and short term treatment with very low

GH doses (5 mu g/kg for 4 days) on the IGF-I levels in 27 normal elderly

subjects.

Normal young adults (age 21) were studied as controls. The starting IGF-I levels

were lower in elderly group than in

young group (123.1 vs. 230.4 mu g/l). In Group 1, the single administration of

20 mu g/kg GH induced a significant IGF-I

rise both in young (318.0 vs. 256.0 mu g/l) and elderly (187.2 vs. 100.4 9.5 mu

g/l). IGF-I levels after GH in elderly

persisted lower than those in young, but the percentage IGF-I increase after GH

was higher in elderly (91.6%) than in

young (23.9%) subjects. In Group 2, IGF-I levels were significantly increased 12

hours after the first administration of

5 mu g/kg GH both in elderly (166.6 vs. 138.3 mu g/l) and young (272.2 vs. 230.4

mu g/l). Twelve hours after the last GH

administration, IGF-I levels were further increased both in elderly (to 208.7 mu

g/l) and in young (to 301.7 mu g/l).

IGF-I levels in elderly persisted lower than those in young at each time point;

however, the percentage IGF-I increase

after GH in elderly and young was similar (after the first administration: 22.4%

vs. 21.7%; after the last

administration: 52.9% vs. 39.5%).

The data demonstrate that IGF-I levels in aging are reduced but the peripheral

sensitivity to GH is preserved. In fact,

in aged subjects the percentage GH-induced IGF-I increase is similar or even

higher than that in young controls.

The findings also indicate that a very low GH dose is needed in aged subjects to

restore IGF-I levels to the young

range.

CLINICAL ENDOCRINOLOGY, 1998, Vol 49, Iss 6, pp 757-763

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Good health & long life,

Greg ,

http://optimalhealth.cia.com.au