Insulin-like growth factor-1 is associated with regulation of the luteinizing hormone production in men receiving androgen deprivation therapy with gonadotropin-releasing hormone analogues for localized prostate cancer.

BACKGROUND

Luteinizing hormone (LH) during androgen-deprivation therapy (ADT) with gonadotropin-releasing hormone analogues (GnRHa) has been thought to be biologically inactive, and the regulation of LH during ADT with GnRHa is thus unknown. Insulin-like growth factor-1 (IGF-1) is involved in the regulation of cell proliferation and differentiation, and IGF-1 production in the liver is dependent on growth hormone (GH) secretion from the anterior pituitary. Despite the presence of IGF-1 receptors in the gonadotroph, associations between the GH/IGF-1 and pituitary-gonadal axes, e.g., whether IGF-1 elicits the LH secretion, remain unclear.

METHODS

Seventy-one patients with localized prostate cancer, who received ADT with GnRHa, were prospectively studied based on their blood samples before treatment and after ADT for 6 months. We employed highly sensitive assays for measurement of serum testosterone (electrochemiluminescence immunoassay), GH/IGF-1 (radioimmunoassay), adrenocorticotropic hormone (ACTH: immunoradiometric assay), LH (chemiluminescent immunoassay), and dehydroepiandrosterone sulfate (DHEA-S: chemiluminescent enzyme immunoassay).

RESULTS

No correlation was noted between the pretreatment LH and IGF-1 levels; after ADT, the serum LH level was closely correlated with the IGF-1 concentration [Spearman's correlation coefficient (rs) = 0.370, P = 0.001]. The serum levels of androgens and gonadotropins reduced following ADT (P < 0.001 in all). The serum IGF-1 level increased (22 ± 6 nmol/L) compared with that at the baseline (19 ± 5 nmol/L) (P < 0.001), but no change was observed in the serum GH concentration between before and after ADT (1.4 ± 2.3 vs. 0.9 ± 0.9 μg/L, respectively, P = 0.691). The serum testosterone level was not correlated with the LH level either before or after ADT. The testosterone and DHEA-S levels after ADT were correlated with ACTH concentration (rs = 0.367, P = 0.002 and rs = 0.354, P = 0.002, respectively). We did not identify any correlations between the serum IGF-1 concentration and Gleason score, PSA value, or androgen levels.

CONCLUSIONS

During ADT with GnRHa, IGF-1 possibly promotes LH production, although its role is unclear. Associations among pituitary-gonadal, pituitary-adrenal, and GH/IGF-1 axes represented by IGF-1-mediated LH secretion and ACTH-mediated androgen synthesis are of interest, since both prostate epithelium proliferation and male anabolic activity are involved in these 3 axes. Assessment of oncologic outcomes is warranted for their significance in patients with prostate cancer.