The evidence for the lower temperature of the testes of many mammals is summarized, and the reasons suggested for the descent of the testes into a scrotum are discussed. Descriptions are given of the various techniques used for studying the effects of heat on the testis, whole body heating, local heating of the testes (by inducing cryptorchidism, scrotal insulation or immersion of the scrotum in a water bath), and heating of tissue or cell preparations in vitro. The effects of heat are discussed, effects on the testis (weight, histology, physiology, biochemistry and endocrinology), on the numbers and motility of spermatozoa in rete testis fluid and semen, on fertilizing ability of spermatozoa and on the subsequent development of the embryos produced when spermatozoa from heated testes are used to fertilize normal ova. The possible mechanisms for the damaging effects of heat are discussed, as well as the importance of heat-induced abnormalities in male reproduction in domestic animals and humans.

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The Parkes Lecture. Heat and the testis

Varicoceles are found in 19 to 41% of infertile men, and is one treatable form of male infertility. The mechanism by which varicoceles cause the variable effect on male infertility and spermatogenesis is still unknown. Experimental animal models play a useful (but limited) role due to the sudden and variable iatrogenic nature of the varicoceles and the duration of the studies. Much of the human data are derived by the characterization of associated differences in measurable parameters between men with and without varicoceles. The role of hyperthermia, testicular blood flow and venous pressure changes, reflux of renal/adrenal products, hormonal dysfunction, autoimmunity, defects in acrosome reaction, and oxidative stress, in the pathophysiology of varicocele will be discussed.

/pdf/varicocele-and-male-infertility-part-ii-pathophysiology-of-4r84ozrj3c.pdf

Varicocele and male infertility: Part II: Pathophysiology of varicoceles in male infertility

https://www.fertstert.org/article/S0015-0282(11)00003-3/pdf

The Great Debate: Varicocele Treatment and Impact on Fertility

Authors' conclusions The body of the reviewed literature on cryptorchidism comprise primarily fairand poor-quality studies, which limits our ability to draw definitive conclusions. No specific imaging technique is able to completely identify anorchia or position of the undescended testicles and thus eliminate the need for further surgical evaluation. Accuracy of imaging is related to location of the testicles, with less invasive methods demonstrating poor accuracy for abdominally located testicles and those that are atrophied. Hormonal stimulation testing may predict anorchia, but evidence is insufficient, with only two studies of fewer than 50 participants. Hormonal treatment is marginally effective relative to placebo, but it is successful in some children and has minimal side effects, suggesting that it may be an appropriate trial of care for some patients. Surgical options are effective, with high rates of testicular descent (moderate strength of evidence for Fowler-Stephens procedures, high for primary orchiopexy). Comparable outcomes occur with laparoscopic and open approaches.

Evaluation and Treatment of Cryptorchidism

The precise mechanism of the hypospermatogenesis associated with varicocele has remained uncertain, although there have been a number of speculations on the etiology of the associated infertility. ...

https://www.tandfonline.com/doi/pdf/10.3109/01485018908986765

Biochemical Changes in Testicular Varicocele

To study the effect of temperature on human spermatogenesis, both the number and DNA synthesis of germ cells were investigated in tissue fragments of human testes cultured for 22 h at 31 degrees C and 37 degrees C. The number of differentiated germ cells such as spermatids and spermatozoa cultured at 37 degrees C was significantly smaller than that cultured at 31 degrees C. The number of spermatogonia and resting primary spermatocytes was not significantly different between these two temperatures, but the functional ability of DNA synthesis in these cells was significantly lower at 37 degrees C than at 31 degrees C. It seems that in normal body temperature (37 degrees C) differentiated germ cells such as spermatids and spermatozoa are fragile and the DNA synthesis of spermatogonia and resting primary spermatocytes is retarded.

https://www.tandfonline.com/doi/pdf/10.3109/01485018708986808

Temperature sensitivity of human spermatogonia and spermatocytes in vitro.

The operative treatment for surgical repair of bilateral testicular varicoceles was evaluated in terms of the improvement achieved in the sperm density and percentage progressive motile sperm. These parameters were compared for 27 cases of bilateral varicocele diagnosed by palpation and subjected to bilateral high ligation of the internal spermatic vein and for 40 cases of left unilateral testicular varicocele. There were no significant differences in preoperative values (such as sperm density; progressive motile sperm; serum levels of luteinizing hormone, follicle-stimulating hormone, and testosterone; and Johnson's score count) between the bilateral and unilateral testicular varicocele groups. The improvement in postoperative sperm density in the cases with bilateral testicular varicocele was apparently less satisfactory than in the cases with testicular varicocele only on the left side.

T Matsui

Papers

Temperature sensitivity of human spermatogonia and spermatocytes in vitro.

Improvement of semen characteristics after surgical repair of bilateral testicular varicocele as compared to unilateral varicocele patients.