Type 1 deiodinase activity and generation of triiodothyronine (T3) in prostate of sexually active rats

Prostate gland as a target organ of thyroid hormones: advances and controversies

Thyroid hormones (THs) are involved in the development and function of the male reproductive system, but their effects on the prostate have been poorly studied. This work reviews studies related to the interrelationship between the thyroid and the prostate. The information presented here is based upon bibliographic searches in PubMed using the following search terms: prostate combined with thyroid hormone or triiodothyronine, thyroxine, hypothyroidism, hyperthyroidism, or deiodinase. We identified and searched 49 articles directly related to the issue, and discarded studies related to endocrine disruptors. The number of publications has grown in the last 20 years, considering that one of the first studies was published in 1965. This review provides information based on in vitro studies, murine models, and clinical protocols in patients with thyroid disorders. Studies indicate that THs regulate different aspects of growth, metabolism, and prostate pathology, whose global effect depends on total and/or free concentrations of THs in serum, local bioavailability, and the endocrine androgen/thyronine context.

Postejaculatory increase of prostatic triiodothyronine (T3) depends on sympathetic innervation in the rat

Thyronines are essential for the development of the male reproductive system, including the prostate gland. Metabolically active 3,5,3' triiodothyronine (T(3)) is generated mainly by the extrathyroidal, enzymatic 5'deiodination of the prohormone thyroxine (T(4)), which is catalyzed by deiodinases type 1 (D1) and type 2 (D2). Prostate D1 activity is highly expressed during puberty and declines with age, but continuous, long-term sexual activity prevents this reduction. The aims of this study were to characterize the changes in prostatic D1 activity in response to consecutive ejaculations and to determine whether sympathetic input participates in the local T(3) generation (D1 activity). D1 activity was analyzed in prostates of sexually experienced, 4-mo-old male rats after one to five ejaculations. D1 activity, T(3) concentrations, and the T(3)-dependent gene ornithine decarboxylase (Odc) were measured after the fourth ejaculation in prostates of intact, sham, and sympathectomized (Smpx, hypogastric nerve) rats. D1 activity was evaluated by the radio-iodine-release method; T(3) was measured by radioimmunoassay and Odc expression by real-time PCR. Data showed a gradual increase of prostate D1 activity in response to consecutive ejaculations. The highest activity was found after the fourth ejaculation, and it decreased after the fifth. The increase of prostate D1 activity after ejaculation was blocked in Smpx males as compared to intact or sham animals. The changes in D1 activity correlate with prostatic T(3) concentrations and Odc expression. Circulating levels of T(3) were not affected by consecutive ejaculations or by Smpx. These findings indicate that the postejaculatory increase in prostatic generation of T(3) depends on sympathetic input.