Competing hypotheses for the etiology of cryptorchidism in Sitka black-tailed deer: an evaluation of evolutionary alternatives

On the Aliulik Peninsula (AP) of Kodiak Island, Alaska, 70% of male Sitka black-tailed deer (SBTD; Odocoileus hemionus sitkensis ) are bilaterally cryptorchid (both testes fail to descend; male is sterile). Both genetic and environmental factors have been proposed as possible causes of this problem. We investigated the possibility that population genetic processes (isolation, inbreeding and genetic drift) have contributed to an increased frequency of cryptorchidism in this population. Overall, SBTD on major islands throughout Alaska have unusually low levels of genetic diversity, though we identified a likely glacial refugium on Prince of Wales Island in the Alexander Archipelago. Within the Kodiak Archipelago, deer on the AP did not exhibit the patterns of genetic isolation, inbreeding and drift that would be expected if cryptorchidism in this population was the result of a founder mutation(s). Instead, our data favor exposure to environmental contaminants as a likely alternative mechanism causing high prevalence of cryptorchidism on the AP.     

Spermatogenesis in azoospermic,formerly cryptorchid men. Use of needle aspiration techniques

OBJECTIVE: To assess the use of testicular needle aspiration techniques to evaluate fertility potential in azoospermic, formerly cryptorchid men. STUDY DESIGN: Fifteen consecutive adult azoospermic, formerly cryptorchid patients (eight unilateral and seven bilateral) were examined by needle aspiration techniques, fine (FNA) and large needle (LNAB) testicular aspiration biopsy, for cytologic and histologic analysis. Five of the 15 subsequently underwent surgical biopsy for attempted assisted fertilization. RESULTS: Spermatozoa or spermatids were detected by FNA cytology or LNAB histology in one or both testicles in 87.5% of the unilateral and 28.6% of the bilaterally affected, formerly cryptorchid patients (P = .041, Fisher's exact test). The addition of LNAB to FNA identified spermatids in one patient with unilateral cryptorchidism and only Sertoli cells on FNA cytology. Furthermore, LNAB differentiated testicles with the cytologic finding of only Sertoli cells into those with or without diffuse fibrosis. In the five patients in whom assisted fertilization was attempted, the needle aspiration techniques predicted the presence or absence of spermatozoa in the subsequent surgical biopsy. CONCLUSION: The two needle aspiration techniques can be used to assess the fertility potential of azoospermic, formerly cryptorchid men and to select patients for assisted fertilization.     

13 Years' experience with the combined hormonal therapy of cryptorchidism.

PURPOSE: We analyze the results of the combined treatment with luteinizing hormone releasing hormone (LH-RH) and human chorionic gonadotropin (HCG) of a large series of patients with cryptorchidism. MATERIALS AND METHODS: Between 1987 and 1999 and after strict differentiation between cryptorchid, retractile and gliding testes, 2,467 boys with 2,962 cryptorchid-gliding testes were treated with the combined hormonal therapy. LH-RH was administrated as a nasal spray at a dosage of 1.2 microg daily for a period of 4 weeks. HCG was injected intramuscularly, 5 times at 2-day intervals at a dosage adjusted according to the age. RESULTS: In the prospective study 2,476 boys with 2,962 cryptorchid testes were hormonally treated. Of the 2,962 evaluated cases 1,200 (40.52%) have been treated surgically after the hormone therapy. In 1,762 cases, 59.48% of cryptorchid testes were in the scrotum after combined hormone treatment. CONCLUSIONS: Treatment with LH-RH and HCG induced the descent of the testes to a normal scrotal position of boys with cryptorchidism in 59.48% of the evaluated cases. The combined treatment was effective for inducing descent of cryptorchid and gliding testes. According to the evaluated intraoperative findings, the failure of the combined therapy in 40.52% of the cases is due to the fact that the free descent is limited by local factors such as anatomical alterations of the inguinal canal, epididymal abnormalities or ectopic distal attachment of the lig. testis.     

Cryptorchidie et température testiculaire

The testis migrates to a scrotal location before birth. This physiological descent is associated with a reduction in the temperature of the testicular environment since the temperature of the scrotal cavity is lower than that of the body one. This leads to the etablishment of a themperature gradient between the testis and the body which already exists in prepubertal boys. In cases of testicular maldescent (cryptorchidism), the temperature of the testis in its cryptorchid location is much higher than that of the normally descended contrlateral testis. However, there are no data obtained from human studies to establish wether the increased temperature of a cryptorchid testis is responsible for the spermatogenic perturbations typically observed. Nor do we know wether the relocation of a cryptorchid testis to the scrotum permits re-establishment of a normal testicular temperature. Adult men with a history of cryptorchidism constitute about 10% of infertile men, and among these previously cryptorchid infertile men 45% have an abnormally elevated scrotal temperature. This abnormal increase in scrotal temperature is a negative risk factor for fertility: these men have smaller testicular volumes, a more severely impaired spermatogenesis and a higher prevalence of primary infertility than previously cryptorchid infertile than previously cryptorchid infertile men with normal scrotal temperature. However, data provided until now do not allow to know whether elevated temperature is due to the decreased testicular size (hypotrophy) or is a consequence of cryptorchidism per se.     

Expression of the NSE,SP,NFH and DβH in normal and cryptorchid testes of Bactrian camel

Neuroendocrine substances play essential roles in regulating the normal physiological functions of testicles. The purpose of this study is to explore the localization and effects of four neuroendocrine markers (NSE, SP, NFH and DβH) in normal and cryptorchid testes of Bactrian camels using western blotting, transmission electron microscopy, immunohistochemistry, and immunofluorescence methods. The results showed that cryptorchidism caused a reduction in layers of spermatogenic epithelium and decreased glycogen positivity in the basement membrane. The ultrastructure revealed that macrophages were always found around the Leydig cells, crowded with swelling mitochondria in cryptorchidism. Expression of NSE in the Leydig cells of cryptorchidism was significantly weakened compared to that in the normal group(p<0.01). We found that SP was always distributed along the nerve fibers in normal testes and was expressed in the Leydig cells of cryptorchidism. However, expression of NFH in the cryptorchidic tissue was strongly positive in the spermatogenic epithelium, with limited expression in Leydig cells and no expression in peritubular myoid cells. Therefore, the expression of DβH in the Sertoli cells was comparatively strong in both the normal and cryptorchidism groups. NFH and DβH expression was significantly increased in the cryptorchidism group compared with the normal group (p<0.01). These findings indicated that the underdeveloped seminiferous epithelium and pathological changes in cryptorchid tissue in Bactrian camels were potentially related to a disorder in glycoprotein metabolism. Our results suggest that NSE and SP could help judge the pathological changes of cryptorchidism. The present study provides the first evidence at the protein level for the existence of NFH and DβH in Sertoli and Leydig cells in Bactrian camel cryptorchidism and provides a more in-depth understanding of neuroendocrine regulation is crucial for animal cryptorchidism.     

Gastrointestinal helminths of free-ranging Florida panthers (Puma concolor coryi) and the efficacy of the current anthelmintic treatment protocol

Thirty-five Florida panthers (Puma concolor coryi [Bangs, 1899]) collected from six counties in southern Florida between 1978 and 2003 were examined at necropsy for gastrointestinal helminths. The panthers were placed into two groups: 1) treated with anthelmintics (n = 17), and 2) untreated (n = 18). Nine species of helminths (one trematode, six nematodes, and two cestodes) were identified in the untreated panthers. The most prevalent helminths were Alaria marcianae (LaRue, 1917) (100%), Spirometra mansonoides (Mueller, 1935) (91%), and Ancylostoma pluridentatum (Alessandrini, 1905) (89%). Ancylostoma caninum (Ercolani, 1859) is reported from the Florida panther for the first time. The intensities of helminths with prevalences >10% did not differ between untreated panthers collected in 1978-1983 and 1996-2003. Treated panthers had helminth faunas similar to those of untreated panthers. The current anthelmintic treatment being used reduced the intensity of both A. marcianae and A. pluridentatum in panthers < or =6 mo posttreatment (PT); however, treated panthers between 6 and 9 mo PT, and >9 mo PT were similar to untreated panthers. Treatment was less effective on S. mansonoides and Taenia omissa Lühe, 1910. Treated panthers had slightly lower intensities of S. mansonoides at < or =6 mo PT; however, between 6 and 9 mo PT and >9 mo PT they had significantly higher intensities than untreated panthers. At all periods PT, the intensity of T. omissa for the treated panthers was similar to that of untreated panthers. We suggest that Mesocestoides sp. may not be present in the Florida panther population as reported earlier by Forrester et al. (1985), due to parasite misidentification by those authors.     

Endocrine and immunological findings in cryptorchid infants

In cryptorchid infants, significantly decreased mean levels of plasma testosterone and luteinizing hormone (LH) were found between the ages of 30 and 120 days. The levels of testosterone and LH were significantly correlated. No significant difference was found between infants with bilateral or unilateral cryptorchidism. After 120 days there was no longer any significant difference between cryptorchid infants and controls. No significant change in plasma follicle-stimulating hormone (FSH) was found. These data suggest that subnormal secretion of LH could be the primary abnormality in a proportion of boys with so-called common cryptorchidism. Our studies using LH-releasing hormone and human chorionic gonadotropin stimulation tests in older infants and children agree with the data obtained by measurement of basal plasma hormone levels during the first months of life. Anti-gonadotroph antibodies were found in the sera of approximately 50% of the cryptorchid children and infants studied, using an immunofluorescence technique. A study of 17 mothers and their infants gave concordant results in 16 pairs, 9 with and 7 without antibodies. This lead us to speculate on the possible role of maternal autoantibodies as a cause of partial gonadotrophin deficiency in the perinatal period and thus of testicular maldescent. As cryptorchidism is a syndrome, these findings do not mean that a similar mechanism is operative in all cases. However, these data do suggest that alternatives to the classical anatomical view of the descent and nondescent of the testes should be considered.     

Cryptorchidism: an indicator of testicular dysgenesis?

Cryptorchidism is a common ailment of new-born boys, affecting 1–9% of full term boys at birth. Cryptorchidism has been associated with an increased risk of testicular cancer and reduced fertility. Aetiology of cryptorchidism remains obscure in most cases. Familial occurrence suggests a heritable susceptibility to cryptorchidism; however, seasonal variation in the incidence of cryptorchidism suggests that environmental factors also contribute. Testicular descent is characterised by androgen-dependent regression of cranial suspensory ligament and androgen + insulin-like hormone 3 (Insl3)-dependent gubernacular outgrowth. Even though hormonal defects are rarely detected in patients, both hypo-and hypergonadotropic hormonal patterns have been associated with cryptorchidism. Moreover, cryptorchid boys have significantly reduced serum androgen bioactivity at 3 months of age when normal boys have a strong surge of reproductive hormones. Defects in Insl3 action cause cryptorchidism in male mice, and over-expression in female mice causes ovarian descent. Defects in leucine-rich repeat-containing G-protein-coupled receptor 8/G-protein-coupled receptor affecting testis descent (LGR8/GREAT), the receptor for Insl3, manifest the same phenotype as Insl3 knockout mutants. Even though mutations found in Insl3 and LGR8/GREAT genes are not a common cause of cryptorchidism in patients, it remains to be resolved whether low Insl3 levels during development are associated with cryptorchidism. Cryptorchidism may reflect foetal testicular dysgenesis that may later manifest as subfertility or testicular cancer.This work was supported by the Turku University Central Hospital, the Academy of Finland and the European Commission (contracts BMH4-CT96-0314, QLK4-CT1999-01422, QLK4-CT2001-00269 and QLK4-CT2002-00603).     

Pathogenesis of cryptorchidism.

Cryptorchidism was induced experimentally by treating pregnant mice on the 14th day of pregnancy with 5 mg estrogen. Testes from cryptorchid and control newborn and adult mice were investigated with radioimmunoassay and electron microscopy. It was concluded that a normal Leydig cell function plays a decisive role in testicular descent. In cryptorchidism, Leydig cells at birth are atrophic. Testicular testosterone content is diminished as compared to controls. Ultrastructural alterations of Leydig cells observed in our experiments closely resemble those found in biopsies of cryptorchid patients. In male mouse offspring, prenatal estrogen injection induced not only a cryptorchidism but also Leydig cell atrophy and a permanently impaired function. Testosterone content is still significantly diminished after puberty. It is proposed therefore that an insufficiency of endocrine gonadal function of hypothalamo-pituitary origin occurring during intrauterine development is one of the main causes of cryptorchidism. An appropriate long-term therapy could diminish the high sterility rate.     

Environmental effects on hormonal regulation of testicular descent

Regulation of testicular descent is hormonally regulated, but the reasons for maldescent remain unknown in most cases. The main regulatory hormones are Leydig cell-derived testosterone and insulin-like factor 3 (INSL3). Luteinizing hormone (LH) stimulates the secretion of these hormones, but the secretory responses to LH are different: INSL3 secretion increases slowly and may reflect the LH dependent differentiated status of Leydig cells, whereas testosterone response to LH is immediate. Testosterone contributes to the involution of the suspensory ligament and to the inguinoscrotal phase of the descent, while INSL3 acts mainly in transabdominal descent by stimulating the growth of the gubernaculum. INSL3 acts through a G-protein coupled receptor LGR8. In the absence of either INSL3 or LGR8 mice remain cryptorchid. In humans only few INSL3 mutations have been described, whereas LGR8 mutations may cause some cases of undescended testis. Similarly, androgen insensitivity or androgen deficiency can cause cryptorchidism. Estrogens have been shown to down regulate INSL3 and thereby cause maldescent. Thus, a reduced androgen–estrogen ratio may disturb testicular descent. Environmental effects changing the ratio can thereby influence cryptorchidism rate. Estrogens and anti-androgens cause cryptorchidism in experimental animals. In our cohort study we found higher LH/testosterone ratios in 3-month-old cryptorchid boys than in normal control boys, suggesting that cryptorchid testes are not cabable of normal hormone secretion without increased gonadotropin drive. This may be either the cause or consequence of cryptorchidism. Some phthalates act as anti-androgens and cause cryptorchidism in rodents. In our human material we found an association of a high phthalate exposure with a high LH/testosterone ratio. We hypothesize that an exposure to a mixture of chemicals with anti-androgenic or estrogenic properties (either their own activity or their effect on androgen–estrogen ratio) may be involved in cryptorchidism.     

GREAT/LGR8 is the only receptor for insulin-like 3 peptide

During male development testes descend from their embryonic intraabdominal position into the scrotum. Two genes, encoding the insulin-like 3 peptide (INSL3) and the GREAT/LGR8 G protein-coupled receptor, control the differentiation of gubernaculum, the caudal genitoinguinal ligament critical for testicular descent. It was established that the INSL3 peptide activates GREAT/LGR8 receptor in vitro. Mutations of Insl3 or Great cause cryptorchidism (undescended testes) in mice. Overexpression of the transgenic Insl3 causes male-like gubernaculum differentiation, ovarian descent into lower abdominal position, and reduced fertility in females. To address the question whether Great deletion complements the mutant female phenotype caused by the Insl3 overexpression, we have produced Insl3 transgenic mice deficient for Great. Such females had a wild-type phenotype, demonstrating that Great was the only cognate receptor for Insl3 in vivo. We have established that pancreatic HIT cells, transfected with the INSL3 cDNA, produce functionally active peptide. Analysis of five INSL3 mutant variants detected in cryptorchid patients showed that P49S substitution renders functionally compromised peptide. Therefore, mutations in INSL3 might contribute to the etiology of cryptorchidism. We have also showed that synthetic insulin-like peptides (INSL4 and INSL6) were unable to activate LGR7 or GREAT/LGR8.     

Fertility after unilateral cryptorchidism. Paternity, time to conception, pretreatment testicular location and size, hormone and sperm parameters.

OBJECTIVE: To further evaluate whether fertility is decreased among a cohort of men with previous unilateral cryptorchidism as compared with a control group of men. SUBJEcTS AND METHODS: Formerly unilateral cryptorchid men who had undergone orchiopexy between the years of 1955 and 1975 at the Children's Hospital of Pittsburgh and a control group of men who were matched for age of an unrelated surgery at the same institution were evaluated by review of medical records and by completion of a questionnaire. 359 previously cryptorchid men were identified as having attempted paternity. Of these men, 320 had information concerning preoperative testicular location and 163 for preoperative testicular size. 106 of these men had levels of testosterone, inhibin B, FSH, and LH measured, while 95 of the men had semen analyses. RESULTS: Among men who had attempted paternity, there was no statistical difference in success of paternity between the previously unilateral group (89.7%) and the control group (93.7%). There was no difference in the mean time to conception (7.1 +/- 0.7 months for the unilateral group vs. 6.9 +/- 2.3 for the control group). Within the unilateral group in regard to success at paternity, no difference was found compared with the age of orchiopexy, preoperative testicular location, or preoperative testicular size. Inhibin B levels were lower among the unilateral group. FSH, LH, testosterone, sperm density, motility and morphology were not different, but considerable variation was noted within the cryptorchid group. CONCLUSIONS: In this continued evaluation of a cohort of previously cryptorchid men who had undergone unilateral orchiopexy, paternity does not appear to be significantly compromised after unilateral cryptorchidism. Unilateral cryptorchidism appears to be one of several factors contributing to infertility, similar to those found in the general population. No correlation was found between success at paternity and the age of orchiopexy, preoperative testicular size or preoperative testicular location. Inhibin B levels were lower while FSH, LH, T and sperm parameters did not differ.     

Effect of LH-RH treatment on hypothalamo-pituitary-gonadal axis and Leydig cell ultrastructure in cryptorchid boys

62 cryptorchid boys aged 2-6 years were selected at random either for surgical or for hormonal LH-RH treatment. As all biopsies from boys operated show typical histological and ultrastructural signs of cryptorchidism, it can be concluded that only true cryptorchid patients are included in our study. LH-RH treatment was successful in 16 (55%) of 31 boys. Median 30-min response values to LH-RH test of LH were initially normal in all boys. Those treated successfully remain normal after treatment whereas unsuccessfully treated patients have significantly lower LH 30-min response values at the end of the 4 weeks of LH-RH treatment. FSH response was not statistically different before or after treatment. This might indicate that a normal LH response is necessary for testicular descent. In the 15 boys operated after 4 weeks of unsuccessful LH-RH treatment, testes biopsies show recruitment of the Leydig cell precursors and development of juvenile Leydig cells with an increase in their content of lipoid droplets and smooth endoplasmic reticulum. No adverse effect on the number of spermatogonia could be observed after 4 weeks of LH-RH treatment.     

Cryptorchidism in free-living jaguar (Panthera onca): first case report

Cryptorchidism is a genital alteration wherein one or both testicles fail to descend into the scrotum and has multifactorial causes. A free-range adult male was captured twice in the Pantanal of Nhecolândia to put a GPS collar and semen collection. Pharmacological semen collection, andrological examination and semen analysis were performed. At the first capture and during the andrological examination only the left testis was found, and the male qualified as cryptorchid. The penis had no penile spines at either procedure. The semen volume obtained at first and second capture was 435 and 160 μL, respectively, with a concentration of 618 and 100 x 10⁶ sperm/mL, progressive motility of ~ 5% and ~ 1% and total morphological sperm abnormalities of 74% and 86%. The male was monitored by a GPS collar, but the signal was lost, making it difficult to re-captures and perform new seminal and ultrasound evaluations to discard monorchidism – exceedingly rare in felids. Genetic studies to assess the individual''s homozygosity are necessary to verify whether cryptorchidism in this individual has a genetic factor.     

Hormonal treatment for unilateral inguinal testis: comparison of four different treatments.

BACKGROUND: Hormonal treatment of cryptorchidism has been used since the 30s, but controversies persist on its efficacy. It is also unclear whether there are differences with the use of different hormonal trials. Aims: To evaluate the efficacy of four hormonal treatments on testicular descent in a homogeneous group of cryptorchid boys. PATIENTS: 155 patients (age 10-48 months) with unilateral inguinal palpable testis were studied. Methods: The patients were subdivided into four groups according to hormonal treatment: group 1 = hCG [500 IU/week (if the chronological age was <2 years) or 1,000 IU/week (if the chronological age was >2 years) for 6 weeks]; group 2 = hCG + hMG (hCG as in group 1 + hMG 75 IU/week for 6 weeks); group 3 = GnRH (1,200 microg/daily for 28 days); group 4 = GnRH + hCG (1,200 microg/daily for 28 days + 1,500 IU/week for 3 weeks, respectively). The results were evaluated at the end of the treatment period and 6 months later to exclude temporarily positive results. RESULTS: At the end of the hormonal therapy, scrotal testicular descent was present in 30 of 155 boys (success rate 19.3%). Seven testes relapsed during follow-up (23.3%). The long-term success rate was 14.8% (23/155 testes). No significant differences were observed in success rates as well as in relapse rates among the four groups. CONCLUSIONS: Hormonal therapy induced permanent testicular descent in a minority of young cryptorchid boys with inguinal palpable testis. Similar results were obtained with four different trials.     

Expression of Hsf1, Hsf2, and Phlda1 in cells undergoing cryptorchid-induced apoptosis in rat testes

Surgery‐induced cryptorchidism, in which the testes are prevented from descending into the scrotal sac, results in testicular germ cell death, and it is commonly used as an experimental tool in the study of spermatogenesis. However, the molecular events underlying the activation of germ cell death remain poorly understood. In the present study, we investigate selective cell loss from cryptorchid rat testis by using DNA flow cytometry and by determining protein and mRNA expression of Hsf1, Hsf2, and Phlda1. The hypo‐haploid cell fraction is significantly decreased as early as 3 days after surgical induction of cryptorchidism (from 42.01 ± 5.74% to 15.98 ± 3.88%), followed by a significant decrease in the haploid cell fraction at Day 7. At the latter time point, an apoptotic peak of spermatocytes appears in DNA histograms just before the tetraploid peak; the percentage of aneuploid cells between diploid and tetraploid rises as high as 14.05 ± 2.98% of the total cells in 7‐day cryptorchid testis, suggesting that a large number of spermatocytes are undergoing apoptosis. The expression of Phlda1 mRNA is significantly elevated 3 days after induction of cryptorchidism. After 7 days of cryptorchidism, Hsf1 and Phlda1 are strongly expressed in the nucleus and cytoplasm, respectively, of primary spermatocytes. Numerous apoptotic spermatocytes are also observed at this time point. These results suggest that the Hsf1/Phlda1 pathway plays an important role in the apoptosis of primary spermatocytes in cryptorchid testis. We present evidence suggesting that Hsf2 is also involved in germ cell removal in cryptorchid testis. Mol. Reprod. Dev. 78:283–291, 2011. © 2011 Wiley‐Liss, Inc.     

Steel-Dickie (Sld) mutation affects both maintenance and differentiation of testicular germ cells in mice.

The effects of Steel-Dickie (Sld) mutations on testicular germ cell differentiation were investigated using experimental cryptorchidism and its surgical reversal in mutant, C57BL/6-Sld/+ and wild-type C57BL/6- +/+ mice. In Sld/+ cryptorchid testes the maintenance of undifferentiated type-A spermatogonia was impaired and their numbers decreased. In contrast, the proliferative activity of type-A spermatogonia in the cryptorchid testis of mutant mice appeared normal as judged by their progression through the cell cycle. Surgical reversal of cryptorchidism resulted in regenerative differentiation of mature germ cells in +/+ testes. However, the regenerative differentiation of type-A spermatogonia which remained in Sld/+ cryptorchid testes was strongly impaired, particularly at two steps of cellular differentiation, from type-A spermatogonia to intermediate or type-B spermatogonia and at meiotic division. Furthermore, in mutant mice, no significant recovery of testicular weight was observed after surgical reversal compared with +/+ mice.     

The genetic rescue of the Florida panther

We examine the consequences of panthers introduced from Texas into south Florida, an area housing a small, isolated, inbred and distinct subspecies ( Puma concolor coryi ). Once part of a continuous, widespread population, panthers became isolated in south Florida more than a century ago. Numbers declined and the occurrence of genetic defects increased. Hoping to reverse the genetic damage, managers introduced eight female panthers from Texas into south Florida in the mid-1990s. This action was highly controversial and we explain the arguments for and against the intervention. We synthesized data systematically collected on the Florida panthers from before, during and after this management intervention. These data include information on movements, breeding, mortality, survivorship and range. There is no evidence that purebred Florida females produce fewer kittens at a later age or less often than do hybrid cats (i.e. those with a Texas ancestor). Hybrid kittens have about a three times higher chance of becoming adults as do purebred ones. Hybrid adult females survive better than purebred females; there is no obvious difference between the males. Males die younger than females, are more often killed by other males and are more likely to disperse longer distances into habitats that are dangerous to them. Hybrids are expanding the known range of habitats panthers occupy and use.     

Cryptorchidism in North American cattle: breed predisposition and clinical findings

The authors analyzed data collected over 26 years from 143 cryptorchid bulls admitted to 23 North American veterinary schools. Breed was found to be a risk factor. The medical records of 41 cryptorchid cattle were also obtained, and the physical examination findings, method of diagnosis, and surgical management were recorded. Polled Hereford and Shorthorn cattle were at significantly greater risk for cryptorchidism; however, polled cattle were not at an increased risk for cryptorchidism. Cryptorchidism was most commonly diagnosed by external palpation of the superficial inguinal rings and by palpation per rectum. Unilateral cryptorchidism appears to be more common than bilateral cryptorchidism. The incidence of cryptorchidism was 69% for the left testis and 31% for the right testis. Sixty-six percent of the retained testes were located in the inguinal canal. Cryptorchidectomy was performed through an inguinal, paramedian or flank approach in 26 bulls. Cryptorchidism appears to be rare in bovine bulls admitted to North American veterinary schools, with 1.7 cases per 1,000 bull admissions. We suggest that cryptorchidism be considered an inherited trait in the Shorthorn and Polled Hereford breeds.