Growth hormone responses to growth hormone-releasing factor (1-29) in euthyroid, hypothyroid and hyperthyroid rats.
In order to investigate whether the impaired GH secretion associated with hypothyroidism and hyperthyroidism is due to a hypothalamic or a pituitary disorder, we have studied plasma GH responses to GH-releasing factor (1-29) (GRF) in euthyroid, hypothyroid and hyperthyroid rats. Hypothyroid rats showed a significant (P less than 0.001) reduction in GH responses to GRF (5 micrograms/kg) at 5 min (350 +/- 35 vs 1950 +/- 260 micrograms/l), 10 min (366 +/- 66 vs 2320 +/- 270 micrograms/l) and 15 min after GRF injection (395 +/- 72 vs 1420 +/- 183 micrograms/l; mean +/- S.E.M.) compared with euthyroid rats. Hyperthyroid rats showed a significant (P less than 0.05) decrease in GH responses to 5 micrograms GRF/kg after 30 min (200 +/- 14 vs 325 +/- 35 micrograms/l) but not at other time-points, or after the administration of 1 microgram GRF/kg. These data indicate that in hypothyroidism and perhaps hyperthyroidism there is an alteration in the responsiveness of the somatotroph to GRF administration.
Dieguez
C
C
Jordan
V
V
Harris
P
P
Foord
S
S
Rodriguez-Arnao
M D
MD
Gomez-Pan
A
A
Hall
R
R
Scanlon
M F
MF
D000818:Animals; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D006980:Hyperthyroidism / Q000097:blood / Q000503:physiopathology*; D007031:Hypothalamus / Q000503:physiopathology; D007037:Hypothyroidism / Q000097:blood / Q000503:physiopathology*; D008297:Male; D010446:Peptide Fragments / Q000494:pharmacology*; D010902:Pituitary Gland / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D017337:Sermorelin; D013961:Thyroid Gland / Q000502:physiology; D013972:Thyrotropin / Q000097:blood
D010446:Peptide Fragments; D017337:Sermorelin; D013972:Thyrotropin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone