Hypothalamic-pituitary-testicular function in men with PRL-secreting tumors

Exercise and male factor infertility

Recent advances in the study of andrology are unfolding some of the idiopathic components of male factor infertility. The inclusion of exercise training as a component of male factor infertility has been proposed secondary to changes observed in the reproductive hormone and semen profile of some endurance trained male athletes. Evidence exists that a subset of endurance trained men, particularly runners, present with subclinical changes in their reproductive hormone profile. These changes include a reduction in total and free testosterone, alterations in luteinising hormone release and alterations in pituitary responses to gonadotrophin-releasing hormone and other pharmacological perturbations. Less attention has been directed towards identifying changes in spermatogenesis and fertility capacity as a result of endurance training. The semen ejaculate of some endurance trained athletes presents with nonspecific modifications including a low normal sperm count, decreased motility and several morphological changes that may compromise fertility. Thus, although a subset of high mileage endurance trained runners present with subclinical modifications in their reproductive hormone and semen profile, to date there is no evidence that endurance training causes male infertility. Future investigations should focus on the clinical impact these hormone and semen alterations may have on fertility capacity in endurance trained athletes.

Ultrastructural lesions in testes from hyperprolactinemic men

Testicular tissue from eight men with prolactinomas and elevated serum prolactin were evaluated by light (LM) and transmission electron microscopy (TEM). A semiquantitative assessment of testicular morphology was employed to provide a morphology index for each tissue specimen. Although in each biopsy specimen germ cell exfoliation was evident, as was abnormal structural change in the seminiferous epithelium, there was no apparent correlation with the overall degree of tissue pathology (morphology index) and the serum level of prolactin. All of the tissue displayed variably thickened seminiferous tubule walls which, when viewed by TEM, were composed of thickened laminae propriae and redundant and involuted basal laminae. Likewise, all tubules contained Sertoli cells with overt cytoplasmic degeneration, principally in the apical (adluminal) region of the cell. This was visualized, in part, as a retraction of the apical cytoplasm from periluminal spermatids and degeneration or absence of Sertoli-germ cell junctional specializations. Sertoli-Sertoli cell junctional complexes appeared structurally intact. Leydig cell ultrastructure was typical of normal cells and contained a variable amount of lipid and smooth endoplasmic reticulum. This also was without positive correlation with the overall degree of tissue pathology or level of serum prolactin. Our results demonstrate the variable degree of testicular pathology associated with hyperprolactinemia in man, and suggest that abnormal tubule walls and altered Sertoli cell ultrastructure are consistent findings in this abnormal endocrine condition.

Effect of long term administration of ovine prolactin on hypothalamic-pituitary testicular axis in rat

The effect of hyperprolactinaemia on testicular morphology and on hypothalamic-pituitary-testicular axis was studied in adult male Wistar rats. Animals received ovine prolactin (oPRL) 200 micrograms twice daily s.c.) for 24 and 36 days and were killed by exanguination. Blood was collected for hormonal determinations and sex accessory glands were removed for histological studies. Circulating testosterone (T) and luteinizing hormone (LH) levels showed a significant reduction after 36 days of treatment whereas plasma follicle-stimulating hormone (FSH) levels were unchanged in all animals. No macroscopic or light microscopic histological modifications were observed in the testes. The present results, while excluding a direct effect of hyperprolactinaemia on seminiferous tubules, suggest that LH suppression is the consequence of a central effect of the ovine PRL long-term administration. The increased DA turnover in the hypothalamus suggested as inhibitory on GnRH neurons could account for this effect. The reduction of T levels seems to be mediated by the LH suppression, even though a direct effect of oPRL on Leydig cell receptors could be hypothesized.