Case Presentation: An 18-year-old male presented to our endocrinology clinic with concerns for low libido for one year. He reported extreme fatigue, loss of erections, and sexual desire. The patient was training vigorously for wrestling. He would exercise and weight train for two hours daily on a very limited calorie intake. He started feeling extremely fatigued with difficulty exercising due to muscle weakness. Physical examination revealed a BMI of 19 and tanner stage 3. Vital signs were significant for BP of 86/56mmHg and heart rate of 45 bpm. His testicular volume was 8cc bilaterally (normal 12-19cc). Laboratory work revealed suppressed FSH/LH (0.7/0.2IU/L) and low testosterone levels (21.1Ing/dl). Further workup revealed normal TSH, ACTH, IGF-1, prolactin levels, cosyntropin stimulation test, and urinary drug screen. Pituitary MRI was normal. The patient was advised to increase carbohydrate intake and decrease exercise to 30 minutes daily. With these changes, he managed to gain seven pounds in two months and started noticing erections at night and improvement in libido. On six months follow up, he gained 14 pounds since the presentation. He endorsed normal libido, erections, and much more improvement in energy. On physical examination, both right and left testicular volume increased to 12-15cc. FSH increased to 2.3, LH 1.3, and total testosterone level 452.4 (ng/ml). The patient has now fully recovered.

Discussion: Calorie restriction and overtraining are seen as an increasing trend in young men. These can lead to detrimental effects on the gonadal axis. In 2014, International Olympic Committee recognized this condition as “Relative Energy Deficit in Sport” encompassing both male-female reproductive system disruptions. Historically, the idea of low energy status as being associated with the low testosterone in exercising men was alluded to in the 1980s (1). Approximately 30% of young people with Avoidant and Restrictive Food Intake Disorder are men, still, the research literature is very limited (2). RED-S is a syndrome that results from energy deficits in athletes. If more energy is expanded via exercise than is consumed in a diet, a state of low energy availability occurs, which increases the risk of RED-S development. Diagnosing RED-S may be challenging as symptoms are subtle in men. A detailed exercise and dietary history are key. The energy deficit associated hypogonadism is due to central suppression of the gonadal axis. Some studies show that reduced leptin blunts GnRH pulsatility (3). Conversely, ghrelin increases and is postulated to raise growth hormone and ACTH causing hormonal stress-associated energy deficit. In some clinical studies, energy deficits are associated with increased inflammatory cytokines that suppress the gonadal axis (4). The influencing variables are not well understood but likely to be multifactorial. Therapy should focus on reversing the existing energy deficit to achieve a healthy body weight by limiting intense physical activity.

Conclusions: • The male reproductive axis is very sensitive to energy deprivation• Screening for RED-S should be considered as part of the annual health exam in athletes• Recovery with weight gain suggests that the gonadal axis suppression is functional and reversible