The first study on mice used a human dosage equivalent of about 10 milligrams for a person weighing 60 kilograms or 130 pounds. The researchers found that methylphenidate abolishes testosterone levels, impairs fertility and reduces the number of Leydig cells, which produce testosterone. The higher dosage, equivalent to around 50 milligrams, lowered testosterone less than the smaller dosage. The researchers posited many possible avenues for methylphenidate’s testosterone-lowering effects, but one of the most obvious suggested the drug’s anoretic (appetite-reducing) effects and subsequent lowered caloric intakes, which they argue permanently suppresses pubertal growth in adolescents prescribed the drug. Since dopamine possible that methylphenidate’s dopamine-like effects support testosterone production, whereas a suppression of appetite.11. Fazelipour S, Jahromy MH, Tootian Z, Kiaei SB, Sheibani MT, Talaee N. The Effect of Chronic Administration of Methylphenidate on Morphometric Parameters of Testes and Fertility in Male Mice. J Reprod Infertil. 2012;13(4):232-236.
Weight loss caused by reduced food intake can severely affect growth and pubertal development by perturbing the maturation of not only the hypothalamo –pituitary– gonadal axis but also the axes of the hypothalamus and pituitary with the adrenals, thyroid, and growth hormone.11. Fazelipour S, Jahromy MH, Tootian Z, Kiaei SB, Sheibani MT, Talaee N. The Effect of Chronic Administration of Methylphenidate on Morphometric Parameters of Testes and Fertility in Male Mice. J Reprod Infertil. 2012;13(4):232-236.
However, a study on rats has shown that gavages of hydrochloride cocaine (15 mg/kg), which is structurally similar to MPH, prescribed for 100 days, resulted in testicular weight reduction (12). This study showed the significant reduction of the number of leydig cells in the treatment groups compared with the control group. Some other reports, confirming this finding, have indicated that intraperitoneal injection of hydrochloride cocaine at a dose of 30 mg/kg could cause necrosis and also decrease in the number of interstitial cells of the testes (18). Serum Testosterone secretion showed a significant reduction in the treatment groups of this study. A similar study on the short term effects of MPH on the production of sex-hormone in male mice showed that exposure of mice to MPH causes considerable reduction in testosterone production…” (Fazelipour, et al., 2012). Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3719348/
In another study, pre-pubescent children took an average mean daily dosage of 18 milligrams of methylphenidate for a period of four weeks, but they experienced no change in testosterone levels.
Findings suggest that short-term treatment with methylphenidate at usual doses does not significantly alter salivary testosterone levels in attention-deficit/hyperactivity disorder patients.21. Wang L-J, Chou M-C, Chou W-J, et al. Does Methylphenidate Reduce Testosterone Levels in Humans? A Prospective Study in Children with Attention-Deficit/Hyperactivity Disorder. Int J Neuropsychopharmacol. 2016;20(3):219-227. doi:10.1093/ijnp/pyw101
The second study study, done on adolescent primates, specifically Rhesus monkeys, The first study shows that methylphenidate lowers luteinizing hormone (LH) and interferes with the normal menstrual cycle but also could be responsible for its well-known neuroprotective effects.
“Chronic methylphenidate administration during adolescence perturbs pubertal onset, adversely affects maturation of the female reproductive axis by retarding pituitary LH release, and adversely affects ovarian folliculogenesis. These novel findings may have significant clinical implications in evaluating the effects of methylphenidate abuse on adolescent health.” Reference: https://www.ncbi.nlm.nih.gov/pubmed/16210004
Now, in isolation, a drug’s effect on testosterone tells you little about its desirability in the context of overarching hormonal health.
Dr. Peat has mentioned luteinizing hormone’s contribution to both dementia and cancer.
Dr. Raymond Peat has mentioned caffeine as a treatment from attention-deficit hyperactivity disorder (ADHD), as the drug has a similar effect in the brain as methylphenidate. Caffeine has been shown to have anxiogenic (anxiety-producing effects), whereas methylphenidate (the extended-release version) has been shown to actually improve social anxiety in adults with ADHD.
“The relationship between social anxiety disorder (SAD) and attention-deficit/hyperactivity disorder (ADHD) is a subject which has recently become a topic of interest for research.
In this study, 20 patients with comorbid SAD and adult ADHD who were treated with extended-release methylphenidate monotherapy were evaluated retrospectively.
Clinical response for both ADHD and SAD symptoms was observed in 17 of 20 patients. Overall, one patient did not respond to treatment and two patients dropped out of treatment at the beginning due to adverse effects.
Extended-release methylphenidate improved both SAD and ADHD symptoms and was generally well tolerated. Further studies are required to investigate the relationship between SAD and ADHD.”
Koyuncu, Ahmet, et al. “Extended-Release Methylphenidate Monotherapy in Patients with Comorbid Social Anxiety Disorder and Adult Attention-Deficit/Hyperactivity Disorder: Retrospective Case Series.” Therapeutic Advances in Psychopharmacology, vol. 7, no. 11, Nov. 2017, pp. 241–47. PubMed Central, doi:10.1177/2045125317714193.