Seasonal variations in cryptorchidism

Viral infections that alter estrogen levels during pregnancy may contribute to the etiology of cryptorchidism

Cryptorchidism is as common as type 2 diabetes or celiac disease. Boys with congenital cryptorchidism are at increased risk of infertility and testicular cancer. Zika syndrome, which affects pregnant women, is associated with a high incidence of undescended testes in the infant, accompanied by epididymal anomalies. Zika and influenza virus infections during pregnancy trigger a strong anti-inflammatory immune response and elevated estradiol levels. Elevated estradiol and α-fetoprotein in syncytiotrophoblasts from women who have given birth to cryptorchid boys are indicative of increased estradiol levels in the fetus. Here, I present a hypothesis that hypogonadotropic hypogonadism, cryptorchidism, and retarded epididymal development may be due to elevated fetal estradiol levels caused by viral infection during pregnancy.

Cryptorchidism after the Fukushima Daiichi Nuclear Power Plant accident:causation or coincidence?

Cryptorchidism (undescended testes) is among the most common congenital diseases in male children. Although many factors have been linked to the incidence of cryptorchidism, and testicular androgen plays a key role in its pathogenesis, the cause remains unknown in most cases. Recently, a Japanese group published a speculative paper entitled, "Nationwide increase in cryptorchidism after the Fukushima nuclear accident." Although the authors implicated radionuclides emitted from the Fukushima accident as contributing to an increased incidence of cryptorchidism, they failed to establish biological plausibility for their hypothesis, and glossed over an abundance of evidence and expert opinion to the contrary. We assessed the adequacy of their study in terms of design setting, data analysis, and its conclusion from various perspectives. Numerous factors must be considered, including genetic, environmental, maternal/fetal, and social factors associated with the reporting of cryptorchidism. Other investigators have established that the doses of external and internal radiation exposure in both Fukushima prefecture and the whole of Japan after the accident are too low to affect testicular descent during fetal periods;thus, a putative association can be theoretically and empirically rejected. Alternative explanations exist for the reported estimates of increased cryptorchidism surgeries in the years following Japan's 2011 earthquake, tsunami, and nuclear crisis. Data from independent sources cast doubt on the extent to which cryptorchidism increased, if at all. In any case, evidence that radionuclides from the Fukushima Daiichi Nuclear Power Plant could cause cryptorchidism is lacking.

Risk factors for cryptorchidism

Undescended testis - known as cryptorchidism - is one of the most common congenital abnormalities observed in boys, and is one of the few known risk factors for testicular cancer. The key factors that contribute to the occurrence of cryptorchidism remain elusive. Testicular descent is thought to occur during two hormonally-controlled phases in fetal development - between 8-15 weeks (the first phase of decent) and 25-35 weeks gestation (the second phase of descent); the failure of a testis to descend permanently is probably caused by disruptions to one or both of these phases, but the causes and mechanisms of such disruptions are still unclear. A broad range of putative risk factors have been evaluated in relation to the development of cryptorchidism but their plausibility is still in question. Consistent evidence of an association with cryptorchidism exists for only a few factors, and in those cases in which evidence seems unequivocal the factor is likely to be a surrogate for the true causal exposure. The relative importance of each risk factor could vary considerably between mother-son pairs depending on an array of genetic, maternal, placental and fetal factors - all of which could vary between regions. Thus, the role of causative factors in aetiology of cryptorchidism requires further research.

Cryptorchidism and hypospadias as a sign of testicular dysgenesis syndrome (TDS): environmental connection

Cryptorchidism and hypospadias are common genital birth defects that affect 2-9% and 0.2-1% of male newborns, respectively. The incidence of both defects shows large geographic variation, and in several countries increasing trends have been reported. The conditions share many risk factors, and they are also interlinked to the risk of testis cancer and poor semen quality. Testicular Dysgenesis Syndrome (TDS) may underlie many cases of all these male reproductive health problems. Genetic defects in androgen production or action can cause both cryptorchidism and hypospadias, but these are not common. A monogenic reason for cryptorchidism or hypospadias has been identified only in a small proportion of all cases. Environmental effects appear to play a major role in TDS. Exposure to several persistent chemicals has been found to be associated with the risk of cryptorchidism, and exposure to anti-androgenic phthalates has been shown to be associated with hormonal changes predisposing to male reproductive problems. Despite progress in identification of endocrine-disrupting substances, we are still far from knowing all the risk factors for these birth defects, and advice for prevention must be based on precautionary principles.

Circannual rhythm in the incidence of cryptorchidism in Finland

Conflicting data on circannual variation in birth rates of urogenital malformations have been reported previously. To assess risk factors of cryptorchidism we studied the seasonal variation of cryptorchidism in Finland. We performed a prospective cryptorchidism study in Turku, Finland, from 1997 to 2001 to evaluate the incidence of cryptorchidism. Clinical examinations were performed at birth and at 3 months. Of 9511 liveborn boys (1471 preterm boys) 216 (53 preterm boys) were cryptorchid at birth and 106 (19 preterm boys) at 3 months. The incidence of cryptorchidism was significantly higher in spring (February-April) (3.0%) than in summer (May-July) (1.7%) (OR 1.79; 95% CI: 1.23-2.63). This seasonal difference was observed both among preterm and term boys. We conclude that a circannual fluctuation in the incidence of cryptorchidism exists, which indicates an influence by environmental factors. The underlying reason for cyclicity affects similarly both preterm and term boys.

Cryptorchidism: seasonal variations in Greece do not support the theory of light

To examine seasonal trends of cryptorchidism in Greece, 583 males with true isolated cryptorchidism were analyzed. All 208 912 live-born boys born during the same period were used as a comparison group. Seasonality by month of birth was evaluated using both Edwards' model with adjusted frequencies and exact theta(i), and Walter-Elwood method with exact theta(i). Both tests resulted in consistent findings. The incidence of cryptorchid births in Greece follows a documented cyclic pattern of simple harmonic type with spring being the season of statistical predominance (peak in March with a second, almost equivalent, peak in May). In contrast, in autumn the incidence of cryptorchid births was considerably lower (trough in September). Given the fact that no significant differences in daylight length are found among seasons in Greece, the detection of a significant seasonal variation suggests that factors other than light are involved in the pathogenesis of cryptorchidism. Low environmental temperature is proposed as a causative factor negatively influencing the maternal hCG profiles and the inguinoscrotal phase of testicular descent. This is further supported by: (i) the similarity of our results to those reported by other European countries of different longitude and geographical width and (ii) our data showing significantly smaller maternal hCG profiles at the 26th week of gestation during winter compared with summer.

Prevalence and characteristics of cryptorchidism in a Nigerian district

OBJECTIVE

To determine the prevalence and characteristics of cryptorchidism among primary schoolboys in a Nigerian district.

SUBJECTS AND METHODS

The district selected had 35 primary schools with 23,342 pupils, consisting of 11,275 girls and 11,967 boys. Using a cluster-sampling technique, five primary schools were visited; 1096 boys (aged 5-13 years) participated in the study, giving a sampling ratio of 1:11. The boys underwent a clinical examination of the groin, scrotum and abdomen.

RESULTS

Cryptorchidism was found in nine subjects, giving a prevalence rate of 0.82%. All the undescended testes were unilateral, of which five were right-sided. Eight of the testes were intracanalicular and one was at the external ring. There were no cases of orchidopexy.

CONCLUSION

The prevalence of cryptorchidism among primary schoolboys in this district of Nigeria was high, at eight per 1000. Delayed diagnosis and treatment remains a problem because of the prevailing socio-economic factors. However, the incidence of cryptorchidism was similar to that reported in other parts of the world.

Cryptorchidism: a prospective study of 7500 consecutive male births, 1984-8. John Radcliffe Hospital Cryptorchidism Study Group

A total of 7441 boys were examined for cryptorchidism at birth and, if present, again at 3 months of age. After excluding boys with severe congenital malformations noted at birth, the cryptorchidism rates at 3 months in babies weighing less than 2000 g, 2000-2499 g, and greater than or equal to 2500 g were 7.7%, 2.5%, and 1.41% respectively. The overall rate was 1.55%. The cryptorchidism rate at birth had increased by 35.1% and at 3 months by 92.7%, over Scorer's rates in the 1950s. Part of these increases may be attributable to differences in neonatal mortality, but the increases in babies weighing 2500 g or more of 50.2% at birth and 77.4% at 3 months are unlikely to be overestimates. At birth 1.92% of boys had bilateral cryptorchidism and 3.0% unilateral cryptorchidism. Boys with cryptorchidism at 3 months were more likely to have hypospadias, a small scrotum, and poor scrotal rugation compared with boys having normally descended testes at birth. Factors predicting descent by 3 months in babies cryptorchid at birth are birth weight, laterality and scrotal size, babies with low birth weight, bilateral cryptorchidism, and normal scrotal size being more likely to have normally descended testes by 3 months. Descent by 3 months was more likely the lower the testis along the normal pathway of descent. The orchidopexy rate at an average age of 3 years was 1.24%. This is substantially lower than in other series and lower than our estimated rate of 2.9% using Hospital In-Patient Enquiry data for England and Wales.

Malignant potential of the cryptorchid testis

A follow-up study of 224 male patients from Rochester, Minnesota, diagnosed with cryptorchidism during the period from 1935 through 1974 was conducted to assess the frequency of subsequent testicular neoplasms. Age-specific rates for testicular neoplasm in this community were used to estimate an expected number for comparison with that observed. Two malignant testicular neoplasms have occurred in this cohort; thus, the standardized morbidity ratio was 11.4 (95% confidence interval, 1.4 to 41.1). Of the 158 patients born in the community, 11% were known to have birth weights of less than 2,500 g, approximately twice the expected occurrence. Increased risks were also noted for inguinal hernia, hypospadias, Down's syndrome, cleft lip or palate (or both), clubfoot, and congenital heart disease, for which the standardized morbidity ratios were 3.6, 4.7, 17.8, 11.3, 11.7, and 2.7, respectively. The increased risk for malignant neoplasms observed in this cohort of patients with cryptorchidism is consistent with that found in earlier studies.

Cryptorchidism: a registry based study in Sweden on some factors of possible aetiological importance

STUDY OBJECTIVE

To examine the epidemiological characteristics of boys with cryptorchidism.

DESIGN

Cohort survey using the Swedish personal identification code and Medical Birth Registry to link cryptorchid boys with their pregnancy and delivery data. They were compared with the total population of male births during the same period.

SUBJECTS

2861 cryptorchid boys born in Sweden between 1973 and 1982 were identified. Of these 437 could not be linked with their Medical Birth Registry information for various reasons, or were excluded because they were under 1 year of age at the end of 1982, leaving 2424 cases for study. The reference population comprised all boys born in Sweden during the same period (n = 458,601).

MEASUREMENTS AND MAIN RESULTS

For each study variable, the observed number of cases among boys with cryptorchidism was compared with the expected number calculated from the whole population. A significant increase in intensity ratio for cryptorchidism was found with the first birth, caesarean section, toxaemia of pregnancy, and certain congenital abnormalities (hypospadias and subluxation of the hip). It was also more common in small for dates infants. There was a seasonal variation in cryptorchidism, with increased incidence in January-March.

CONCLUSIONS

Cryptorchidism may be caused by hormonal influences during pregnancy, which could be affected by utero-placental factors involving placental dysfunction or by daylight hours, through pineal activity.

Cyclical patterns and predictability in infection

Many infections, especially viral infections, show a certain periodicity which can be wholly or partly predictable. It is important to be able to recognize these patterns because anticipating changes in incidence should lead to better diagnosis, treatment and control of infection. In this review patterns of some viral and other infections in England and Wales which have been observed from laboratory reports over a period of 21 years, from 1967 to 1987, are described.

The value of England and Wales congenital malformation notification scheme data for epidemiology: male genital tract malformations

Data from the England and Wales national congenital malformation notification scheme were examined for associations of male genital tract malformations. For some of the malformations comparison of notification rates with the literature suggested gross undernotification. There was also evidence suggesting bias: examination of the relationships of the malformations to birth weight, maternal parity, and maternal age at delivery showed some highly significant trends in risk, most of which were at variance with findings in the literature, and several potential mechanisms for bias could be adduced. Direct investigation is needed, for this and other similar data sets, of the extent and mechanisms of biased undernotification.