Reversibility of long-term effects of GnRH agonist administration on testicular histology and sperm production in the nonhuman primate

Differential effects of depot formulations of GnRH agonist leuprorelin and antagonist degarelix on the seminiferous epithelium of the rat testis

Despite their pharmacologically opposite actions, long-acting depot formulations of both GnRH agonists and antagonists have been clinically applied for treatment of androgen-sensitive prostate cancer. Sustained treatment with GnRH analogues commonly suppresses both the synthesis and release of gonadotropins, leading to depletion of testicular testosterone. To clarify the underlying differences in the effects of GnRH agonists and antagonists on spermatogenesis, we compared histological changes in the seminiferous epithelium after administration of depot formulations of GnRH agonist leuprorelin and antagonist degarelix to male rats. Testicular weight had markedly declined by 28 days after administration of both GnRH analogues, although the testicular weight was decreased more promptly by leuprorelin compared with degarelix. Shortly after administration, massive exfoliation of premature spermatids and anomalous multinucleated giant cells was observed in seminiferous tubules of leuprorelin-treated rats, probably via the initial hyperstimulatory effects on the hypothalamic-pituitary-testicular axis, whereas no discernible changes were found in those of degarelix-treated rats. Long term treatment with both types of GnRH analogues similarly induced a marked reduction in the height of the epithelium and deformation of apical cytoplasm in Sertoli cells, resulting in premature detachment of spermatids from the epithelium. Lipid droplets had accumulated progressively in Sertoli cells, especially in those of degarelix-treated rats. These findings clearly demonstrate the differences in the effects of GnRH agonists and antagonists on the spermatogenic process. This study suggests that an appropriate choice of GnRH analogues is necessary to minimize their adverse effects on spermatogenesis when reproductive functions should be preserved in patients.

Short-term buserelin administration induces apoptosis and morphological changes in adult rat testes

PURPOSE

To investigate the effect of buserelin on gonadal structure and function in adult male rats.

METHODS

Twenty-four adult Wistar male rats were divided into three groups: two treated groups and controls. The first and second treated groups received 300 (low dose) and 500 (high dose) µg/kg buserelin, respectively, and the control group received normal saline. All groups were treated subcutaneously for five days.

RESULTS

The seminiferous tubular epithelial thickness was significant decreased in the treated groups compared with those in the control. There was a significant increase in apoptotic cell death in high dose treated group compared with low dose treated and control groups. No significant difference in serum testosterone level was observed after one month in the three groups.

CONCLUSION

Buserelin induces apoptotic cell death and decreased diameter and epithelium thickness of seminiferous tubules in the adult rat testes.

Endocrine control of spermatogenesis: Role of FSH and LH/ testosterone

Evaluation of testicular functions (production of sperm and androgens) is an important aspect of preclinical safety assessment and testicular toxicity is comparatively far more common than ovarian toxicity. This chapter focuses (1) on the histological sequelae of disturbed reproductive endocrinology in rat, dog and nonhuman primates and (2) provides a review of our current understanding of the roles of gonadotropins and androgens. The response of the rodent testis to endocrine disturbances is clearly different from that of dog and primates with different germ cell types and spermatogenic stages being affected initially and also that the end-stage spermatogenic involution is more pronounced in dog and primates compared to rodents. Luteinizing hormone (LH)/testosterone and follicle-stimulating hormone (FSH) are the pivotal endocrine factors controlling testicular functions. The relative importance of either hormone is somewhat different between rodents and primates. Generally, however, both LH/testosterone and FSH are necessary for quantitatively normal spermatogenesis, at least in non-seasonal species.

Treatment of central precocious puberty

This chapter describes several aspects of the management of treatment in girls and boys with central precocious puberty. Although there is some controversy about the indication for gonadotrophin releasing hormone (GnRH) agonist treatment in the literature, a list of clear indications is presented and monitoring requirements for treatment are discussed with reference to the pertinent literature. The development of clinical, psychological, hormonal, sonographical and auxological parameters that can be expected during GnRH agonist treatment is described in detail. In view of the scant evidence-based knowledge, we review the final outcome of patients treated with GnRH agonists with respect to reversibility of hormonal suppression, reproductive function, final height and side effects. The data published so far show that GnRH agonist treatment using the modern depot preparations is not only convenient but also safe, with relatively minor side effects. The outcome in terms of final height is favourable in the majority of patients.

Normal gonadal functions and fertility after 23 months of treatment of prepubertal male and female dogs with the GnRh agonist [D-Trp6, des-Gly-NH2(10)]GnRH ethylamide

The GnRH agonist [D-Trp6, des-Gly-NH2(10)]GnRH ethylamide was administered to prepubertal male and female dogs daily for 23 months by subcutaneous injection. During GnRH agonist treatment, plasma steroid levels, namely dehydroepiandrosterone, androst-5-ene-3 beta-17 beta-diol, androstenedione, testosterone, dihydrotestosterone, 5 alpha-androstane-3 alpha, 17 beta-diol, 5 alpha-androstane, 3 beta, 17 beta-diol were markedly inhibited in male animals, whereas in female animals, the plasma concentration of DHEA and delta 5-diol were decreased. Within 2 months following cessation of therapy, all steroids increased to normal adult levels. Morphological studies reveal that treatment of male animals with the GnRH agonist is accompanied by a small volume of seminiferous tubules, Leydig cells, and prostate gland, whereas in the ovaries of female animals, there is a large number of primordial follicles, a few primary follicles, but no secondary follicles. In the pituitary gland of animals of both sexes, LH-secreting cells have high levels of glycogen particles in their cytoplasm and tend to be either of normal appearance with dilated rough endoplasmic reticulum (RER) or strongly atrophied with a dark-stained cytoplasm, a contraction of RER, and a decrease in the number of secretory granules. Reticular cells of the connective tissue also show high levels of glycogen particles. After the 14 month recovery period, spermatogenesis has a normal adult appearance, the prostate gland shows a normal secretory epithelium, and secondary follicles are easily observed in the ovary. Gonadotrophs are free of glycogen accumulation, but reticular cells continue to show an accumulation of glycogen particles in their cytoplasm. Two male and two female animals were mated after the recovery period and produced normal offspring with normal fertility. The present results indicate that GnRH agonist treatment achieves a blockade of sexual maturation and that following cessation of treatment, normal pituitary-gonadal functions resume, with apparently normal fertility and normal offspring.