Effect of tamoxifen on GH and IGF-1 serum level in stage I-II breast cancer patients.
OBJECTIVE
Tamoxifen suppresses insulin-like growth factor-1 (IGF-1) plasma levels in early and advanced breast cancer patients. Relationships between tamoxifen (GH) and IGF-1 are complex and not completely described yet. The present investigation was performed to evaluate the effect of acute and chronic tamoxifen administration on GH response to growth hormone-releasing hormone (GHRH), as well as on IGF-1 serum levels.


METHODS
Evaluation of GH after administration of GHRH was performed (a) at baseline, (b) 3 hours after 20 mg oral administration of tamoxifen and (c) after 12 weeks of 20 mg a day oral tamoxifen treatment, in fifteen postmenopausal stage I-II breast cancer patients. IGF-I was measured at baseline and after chronic tamoxifen administration.


RESULTS
The GH response to GHRH was significantly reduced after 12 weeks of tamoxifen 10 mg administered twice a day orally (mean peak 3.2 +/- 0.2 micrograms/l, mean AUC 261.3 +/- 18.2 micrograms/minute p < 0.01 versus basal AUC). A concomitant significant reduction of IGF-1 was observed after 3 months of tamoxifen treatment. Basal pretreatment levels of 113.2 +/- 15.5 micrograms/l were suppressed to 70 +/- 7.9 micrograms/l (p < 0.01).


CONCLUSIONS
Our study confirm the inhibitory effect of tamoxifen on IGF-I and suggested, as shown in previous in vitro data, that its suppression could be directly related to GH reduction in response to GHRH stimulation.
Mandalà
M
M
Division of Medical Oncology, European Institute of Oncology, Via Ripamonti 435, 20141-Milan, Italy. mario.mandala@ieo.it
Moro
C
C
Ferretti
G
G
Calabro
M G
MG
Nolè
F
F
Rocca
A
A
Munzone
E
E
Castro
A
A
Curigliano
G
G
D000368:Aged; D000369:Aged, 80 and over; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000097:blood / Q000188:drug therapy* / Q000473:pathology / Q000601:surgery; D018270:Carcinoma, Ductal, Breast / Q000097:blood / Q000188:drug therapy* / Q000473:pathology / Q000601:surgery; D017024:Chemotherapy, Adjuvant; D003131:Combined Modality Therapy; D004341:Drug Evaluation; D004965:Estrogen Antagonists / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D004967:Estrogens; D005260:Female; D013007:Growth Hormone-Releasing Hormone; D019382:Human Growth Hormone / Q000097:blood* / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D015411:Mastectomy, Modified Radical; D008875:Middle Aged; D009367:Neoplasm Staging; D009376:Neoplasms, Hormone-Dependent / Q000097:blood / Q000188:drug therapy* / Q000473:pathology / Q000601:surgery; D017698:Postmenopause / Q000097:blood; D011374:Progesterone; D013629:Tamoxifen / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D016896:Treatment Outcome
D018931:Antineoplastic Agents, Hormonal; D004965:Estrogen Antagonists; D004967:Estrogens; D013629:Tamoxifen; D019382:Human Growth Hormone; D011374:Progesterone; D007334:Insulin-Like Growth Factor I; D013007:Growth Hormone-Releasing Hormone