Exercise-related dysfunction of the hypothalamic-pituitary axis was reported in women decades ago; the condition was called the Female Athlete Triad . Similar dysfunction in males was confirmed 30 years ago. Men who in the past had been running at least 64 km per week had significantly lower serum total testosterone and free testosterone levels than sedentary controls . Subsequent reporting of more cases and the results of clinical trials led renaming of this type of dysfunction as RED-S. RED-S refers to impaired physiological functions, including but not limited to metabolic rate, menstrual function, bone health, immunity, protein synthesis, and cardiovascular health. The cause is energy deficiency due to an imbalance between dietary intake and energy expenditure required for health and activities of daily living, growth, and participation in sporting activities. Psychological sequelae can either precede RED-S or be the result of RED-S . The majority of the literature examining RED-S in males has focused on cyclists, rowers, runners, jockeys, and athletes competing in combat sports; the common thread here seems to be the need to control body weight within strict parameters to optimize performance . There are few reports of RED-S in athletes competing in non-endurance sports. Without large-scale epidemiological studies in this area, data from male athletes is in short supply . The RED-S model considers energy deficiency/low energy availability (LEA) as the central cause[7, 8]. A previous study suggests that a high percentage (47.2%) of male athletes is at high risk for LEA . Research has identified a standard LEA threshold for healthy active women; a diagnosis of LEA in women is based on an energy availability of ≤ 30 kcal/kg·FFM/day . However, no such cut-off point has been identified for exercising men. Therefore, researchers have applied the female-based values to males . Treatment of RED-S involves increasing energy intake, exercise reduction, or a combination of both, along with consultation with a mental health professional if needed .
It is noteworthy that unlike previously reported cases of RED-S, the patient in this case was not competing in an endurance sport [11–13]; indeed, few cases of RED-S have been reported in male non-endurance athletes. Based on his symptoms and signs including low energy, normal phallus and testes, and normal male breast, he was diagnosed with postpubertal onset, secondary hypogonadism . During his 14-day quarantine, he only maintained a basic workout. Decrease of workout may not provide enough training stimuli and result in impaired performance , and possibly trigger RED-S. The patient had very low LEA (10.44 kcal/kg·FFM/day), resulting from reduced caloric intake and increased training intensity. The incidence of LEA in weight-restricted sports is high . In our case, bone density was normal, which is unusual as a common finding in RED-S is loss of bone density . This may indicate that the patient had an acute change. Thyroid hormone levels may have decreased to maintain body energy status, as seen in low T3 syndrome . In addition, release of pituitary prolactin (a testosterone inhibitor) was increased, which is associated with training-induced reductions in testosterone levels . A previous literature review revealed that LEA causes psychological problems when a male athlete approaches the lower limit of BF (4–5%) . Prior to 2019, our patient maintained a low BF level (6%); thus, both low body fat levels and RED-S may have affected his mental health. He recovered after 2 months of reduced intensity exercise and increased caloric intake, which is in line with another study showing that testosterone levels return to normal within 5 weeks of reduced intensity training .
In our case, the patient developed marked hypogonadism after increasing training intensity. Relative malnutrition was caused by excessive energy expenditure and reduced caloric intake. The fatigue and mental health problems were likely due to testosterone deficiency and intensive training. Taken together, the findings reported herein suggest that RED-S can occur in elite male athletes undertaking intense training coupled with restricted caloric intake. Thus, RED-S is not restricted to females and endurance athletes. Therefore, sports scientists/trainers should monitor caloric intake and training intensity to avoid the LEA and RED-S. Such measures will protect the health and improve the performance of all athletes.