Ritalin May Delay Puberty in Boys with ADD and ADHD
The possibility that Ritalin may delay puberty in boys with ADD and ADHD comes from a recent study testing the toxicity of methylphenidate hydrochloride (MPH) - commonly known as the drug Ritalin - on juvenile male rhesus monkeys, which are considered to be a good animal model for pubertal development in man. In the study, juvenile rhesus macaques treated with high doses of MPH were shown to develop a delayed onset of testicular descent - an important indicator of sexual development in males.
Ritalin and ADHD
Ritalin (methylphenidate hydrochloride (MPH)) is a stimulant type drug that affects the chemicals in the brain that contributes to hyperactivity and impulse control problems. Ritalin is typically used to treat children with attention deficit disorder (ADD) and attention deficit hyperactivity disorder (ADHD). ADD and ADHD are medical conditions in which children have difficulties in normal focusing abilities marked by impaired attention and concentration with or without periods of hyperactivity and impulsiveness. Ritalin is also used in the treatment of narcolepsy—a sleep disorder where a person has an uncontrollable desire to fall asleep.
In recent years Ritalin has come under criticism as an over-prescribed medication. According to medical studies, Ritalin prescriptions rose dramatically in the early 1990s and have currently leveled off at approximately 11 million prescriptions per year. Data from the DEA reveals that state-to-state and within communities there is a wide variation in the levels of use of Ritalin implying that there may be both under-prescription and over-prescription of medication for ADHD across the U.S.
The production of Ritalin has soared since 1990 and resulted in a drug abuse problem in the U.S. Under the Controlled Substances Act, the DEA has set quotas regulating the amount of Ritalin that may be produced each year to meet the demands for medical use while ensuring that there is not a surplus of Ritalin that could lead to a black market for its illegal use. According to a report by the United Nations, the U.S. produces and consumes about 85 percent of the world's supply of Ritalin.
Lead author Dr. Donald R. Mattison from the Eunice Kennedy Shriver National Institute for Child Health and Human Development describes an experiment in the journal Proceedings of the National Academy of Sciences (PNAS) that tests the toxicity of Ritalin on rhesus monkeys. In the experiment he treated three groups of monkeys as follows: One group was given a low dose of Ritalin comparable to the dose prescribed for children. A second group was given a high dose of approximately 10 times the amount of the low dose. And a third group was given a control substance lacking the chemical for Ritalin.
What the researchers found was that the high dose of Ritalin resulted in delaying the descent of the testes from the abdomen into the scrotal pouch of adolescent monkeys. The low dose had no effect on testicular descent; however, the low dose and high dose subjects both experienced decreased blood levels of testosterone and abnormally smaller testes.
At the end of the 40-month experiment, however, both the high and low dose test animals had similar sexual development compared to the untreated control animals. Their conclusion was that Ritalin can delay testicular growth and development temporarily in young rhesus monkeys that appears to resolve itself over time as the monkeys develop from the adolescent to the adult stage.
The authors of the paper state in their conclusion that, “The fact that effects were transient and that no permanent deficits were found in the monkey model alleviates concerns about the clinical use of MPH in youth. Finally, we clearly recognize the importance of confirming these findings in additional studies in both animal models and humans.”
While there is no data of obvious harmful effects to extend the study’s results toward human use of Ritalin, the authors contend that research toward this is needed. Rhesus monkeys are considered to be a good animal model of human pubertal development and the authors’ study has not extended toward longer-term effects such as eventual sperm production on the developing testes from the Ritalin doses.
In normal human development, a baby boy’s testicles form inside his abdomen and eventually descend into the scrotum near birth. Sometimes, however, the testicular descent is delayed in a condition known as cryptorchidism—the most common genital abnormality in boys. In roughly 50% of the cases of cryptorchidism, the undescended testicles descend on their own by six months of age.
If the testicles fail to descend, surgical intervention is generally indicated to place the testicles where they belong. The reason why this is important is due to several factors:
• The higher abdomen temperature of the body may interfere with the normal development of the testes, which could impair normal sperm production and lead to future infertility.
• Undescended testicles are at a higher risk of developing a tumor.
• Undescended testicles may be more vulnerable to injury or testicular torsion.
• An unusual appearing or empty scrotum may cause a child worry and embarrassment.
• Boys with undescended testicles may develop inguinal hernias.
If a child’s testes are affected in any way during development, then it appears a genuine concern is reasonable and merits further study toward the safety of Ritalin. An important question that needs to be asked and researched is whether an overprescribing of Ritalin can lead to increased rates of infertility in the U.S.?
Source: “Pubertal delay in male nonhuman primates (Macaca mulatta) treated with methylphenidate” doi: 10.1073/pnas.1102187108 PNAS September 19, 2011 http://www.pnas.org/content/early/2011/09/12/1102187108.full.pdf+html