PROSTATE-THYROID AXIS - STIMULATORY EFFECTS OF VENTRAL PROSTATE SECRETIONS ON THYROID-FUNCTION

BACKGROUND. Endocrine cells of the prostate secrete thyrotropin (TSH)- releasing hormone (TRH), TRH- and TSH-like peptides, and growth factor s. Propylthiouracil- and methimazole-induced hypothyroidism increased prostatic levels of TRH in rats as in hypothalamus, whereas thyroxine (T-4) replacement decreased TRH. From these reports, we inferred the e xistence of a prostate-thyroid axis. METHODS. The influence of the pro state on the thyroid gland was studied in albino rats. Ventral prostat e was surgically removed on day 31 postpartum. The animals were sacrif iced on day 60 postoperation. Serum thyroid hormones were assayed by r adioimmunoassay (RIA). For in vitro studies, normal thyroid and ventra l prostate glands were cocultured with or without thyroid-stimulating hormone (TSH) antibody, to assess the direct influence of prostatic se cretions on thyroid hormone secretion. RESULTS. Serum total and free T -4 and triiodothyronine (T-3) were significantly reduced in ventral pr ostatectomized rats. Histological analysis of the thyroid showed that the diameters of the peripheral and middle follicles, colloid epitheli al cells, and nuclei were increased in prostatectomized rats, indicati ng hypothyroid status. Total T-3 and T-4 were significantly elevated i n the culture medium when thyroid and prostate were cocultured, irresp ective of the presence of TSH antibody. CONCLUSIONS. The present study suggests that ventral prostatic secretions have a stimulatory role on the thyroid gland. Prostate 36:8-13, 1998. (C) 1998 Wiley-Liss, Inc.