Raloxifene lowers IGF-I levels in acromegalic women

IGF-I suppression in acromegaly obtained by tamoxifen, a selective estrogen receptor modulator (SERM), prompted us to evaluate the effects of the administration of a newer SERM, raloxifene (RAL), devoid of estrogenic activity at uterine level, on GH/IGF-I levels in patients with this disease.

Thirteen post-menopausal acromegalic women (aged 55-84 years) with active acromegaly entered a prospective open pilot study of RAL treatment at 60 mg/day. Nine of the patients, who were resistant to somatostatin analog and dopamine agonist treatment, were not undertaking therapy; the other four, who were partially sensitive to medical treatment, maintained treatment at the maximally effective dosages throughout the study.

IGF-I levels fell significantly from 444 (median, interquartile 393-590) microg/l to 300 (216-608) microg/l (P=0.0192) after 1 month of RAL administration and this fall remained stable up to the final evaluation at 5+/-1 months from the start of RAL treatment (260 (187-410) microg/l). An IGF-I decrease greater than 30% of basal values was observed in 10 patients (mainly in patients with IGF-I levels lower than 600 microg/l) and normal values were reached in seven (54%). GH levels did not change (basal 6 (4.1-8) microg/l, final 5.5 (3.2-7.4) microg/l). The clinical picture improved in patients sensitive to RAL. RAL withdrawal was followed by the return of IGF-I levels to pretreatment values within 8 weeks in all patients.

RAL decreases IGF-I levels in most acromegalic women with mild or intermediate disease (i.e. with values lower than 600 microg/l) and normalizes it in many. A prospective randomized study in patients resistant or partially sensitive to other medical treatments is warranted.