Effects of tamoxifen on GH and IGF-I levels in acromegaly.
Tamoxifen (TAM), a non steroid partially competitive antagonist to the estrogen receptors, has been reported to decrease plasma GH and IGF-I levels both in vitro and in vivo. These data prompted us to evaluate GH and IGF-I changes in acromegaly after acute and chronic TAM administration. Nineteen acromegalic patients (6 M, 13 F, aged 30-70 years) were studied in a prospective open study. Acute TAM test (20 mg po) did not induce any significant change in GH and IGF-I levels. Chronic TAM treatment (20 mg/day for a month and 40 mg/day for another month) induced a transient increase in GH levels (from 9 [3-139] micrograms/l [median, range] to 12 [3-188] micrograms/l, p = 0.0025) and a persistent decrease in IGF-I levels (from 785 [500-1200] micrograms/l to 553 [209-1420] micrograms/l, p = 0.0034). Individual IGF-I values decreased in 13 patients and reached the normal range in 4 of them. At TAM withdrawal hormonal levels increased up to pretreatment values. There was no correlation between GH and IGF-I changes and results were not influenced by age, sex or gonadal status. In this setting it is likely that the observed decrease in plasma IGF-I levels is dependent on TAM activity at the hepatic level.
Cozzi
R
R
Divisione di Endocrinologia, Ospedale Niguarda, Italy.
Attanasio
R
R
Oppizzi
G
G
Orlandi
P
P
Giustina
A
A
Lodrini
S
S
Da Re
N
N
Dallabonzana
D
D
D000172:Acromegaly / Q000097:blood / Q000378:metabolism*; D000328:Adult; D000368:Aged; D004965:Estrogen Antagonists / Q000494:pharmacology*; D005260:Female; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013629:Tamoxifen / Q000494:pharmacology*; D013997:Time Factors
D004965:Estrogen Antagonists; D013629:Tamoxifen; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone