Influence of chronic naltrexone treatment on growth hormone secretion in normal subjects.
OBJECTIVE
To verify if a chronic opioid blockade could affect the GH/IGF-I axis.


METHODS
We have investigated the effects of naltrexone (NTX) treatment on GH response to GHRH in normal women.


METHODS
GHRH test (50 micrograms i.v.) performed in seven normal female volunteers (age 25-38 years, with a body mass index ranging from 19.8 to 23.1 kg/m2) before and after 4-weeks NTX treatment (50 mg p.o. daily).


RESULTS
Basal GH, IGF-I, insulin-like growth factor binding protein-3 (IGFBP-3) plasma levels and the IGF-I/IGFBP-3 molar ratio remained unaffected by NTX. NTX significantly reduced the GH peak values (15.52 +/- 3.59 vs 4.78 +/- 0.49 micrograms/l; P < 0.01), and GH area under curve (918.93 +/- 253.96 vs 401.09 +/- 79.63 micrograms/l; P < 0.01).


CONCLUSIONS
This finding suggests that the long-term opioid receptor blockade has an inhibitory role on GHRH-induced GH secretion. A central influence on neurotransmitter control of GH might be hypothesised. The inhibition of stimulated GH release, without interference with the basal level, could indicate an enhanced somatostatin secretion and/or activity. Opioids could be involved only in the regulation of GH dynamics and not in basal secretion. Nevertheless, a direct involvement of opioids at the pituitary level, which could be modified by NTX, cannot be excluded.
Villa
P
P
Department of Internal Medicine II, Catholic University School of Medicine, Rome, Italy.
Valle
D
D
De Marinis
L
L
Mancini
A
A
Bianchi
A
A
Fulghesu
A M
AM
Caruso
A
A
Mancuso
S
S
Lanzone
A
A
D000328:Adult; D019540:Area Under Curve; D005260:Female; D013007:Growth Hormone-Releasing Hormone / Q000008:administration & dosage; D019382:Human Growth Hormone / Q000378:metabolism*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D009271:Naltrexone / Q000008:administration & dosage*; D012636:Secretory Rate / Q000187:drug effects
D018972:Insulin-Like Growth Factor Binding Protein 3; D019382:Human Growth Hormone; D009271:Naltrexone; D007334:Insulin-Like Growth Factor I; D013007:Growth Hormone-Releasing Hormone