In most full-term infant boys with cryptorchidism but no other genital abnormalities, a cause cannot be found, making this a common, sporadic, unexplained (idiopathic) birth defect. A combination of genetics, maternal health, and other environmental factors may disrupt the hormones and physical changes that influence the development of the testicles. * Severely premature infants can be born before descent of testes. Low birth weight is also a known factor. * A contributing role of environmental chemicals called endocrine disruptors that interfere with normal fetal hormone balance has been proposed. The Mayo Clinic lists "parents' exposure to some pesticides" as a known risk factor. * Risk factors may include exposure to regular alcohol consumption during pregnancy (five or more drinks per week, associated with a three-fold increase in cryptorchidism when compared to nondrinking mothers. Cigarette smoking is also a known risk factor. * Family history of undescended testicles or other problems of genital development * Cryptorchidism occurs at a much higher rate in a large number of congenital malformation syndromes. Among the more common are Down syndrome, Prader–Willi syndrome, and Noonan syndrome. * In vitro fertilization, use of cosmetics by the mother, and pre-eclampsia have also been recognized as risk factors for development of cryptorchidism. In 2008, a study was published that investigated the possible relationship between cryptorchidism and prenatal exposure to a chemical called phthalate (DEHP), which is used in the manufacture of plastics. The researchers found a significant association between higher levels of DEHP metabolites in pregnant mothers and several sex-related changes, including incomplete descent of the testes in their sons. According to the lead author of the study, a national survey found that 25% of U.S. women had phthalate levels similar to the levels that were found to be associated with sexual abnormalities. A 2010 study examined the prevalence of congenital cryptorchidism among offspring whose mothers had taken mild analgesics, primarily over-the-counter pain medications including ibuprofen (e.g. Advil) and paracetamol (acetaminophen). Combining the results from a survey of pregnant women prior to their due date in correlation with the health of their children and an ex vivo rat model, the study found that pregnant women who had been exposed to mild analgesics had a higher prevalence of baby boys born with congenital cryptorchidism. New insight into the testicular descent mechanism has been hypothesized by the concept of a male programming window derived from animal studies. According to this concept, testicular descent status is "set" during the period from eight to 14 weeks of gestation in humans. Undescended testis is a result of disruption in androgen levels only during this programming window.
symptom of Empty sella syndrome
symptom of Kallmann syndrome
symptom of Klinefelter syndrome
symptom of Laron syndrome
symptom of Cushing's syndrome
symptom of Hashimoto's thyroiditis
symptom of Rotor syndrome
symptom of Angelman syndrome