It binds to androgen receptors in muscle cells, stimulating the production of proteins and growth factors necessary for muscle development. Testosterone promotes muscle growth by increasing protein synthesis, enhancing muscle fiber growth, and reducing muscle breakdown. By reducing muscle breakdown, testosterone not only maintains existing muscle but also creates a foundation for continued growth, making it a cornerstone of muscle development and maintenance. The starting season consisted mainly of endurance training, strength training and high intensity training. This season is also best for healing injuries and overload of skeletal and muscle systems in participants. Its main focus is moving from specialty rowing training into activities primarily focused on maintaining overall physical activity at an adequate level. It consists of higher intensity training specifically focused on rowing techniques—both tactics-wise and technique needed to develop peak condition in the rower. Written, informed consent form were obtained from all the participants before the beginning of the study. The ethics committee of Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University, in Toruń approved the study protocol and design. According to the renal biopsy, FSGS and ≥ 40% tubular atrophy and interstitial fibrosis were found in nine and three patients, respectively. Additionally, estradiol could affect the dose-dependent action of dihydrotestosterone on the kidneys . Xu et al. demonstrated a dose-dependent relation between administration of exogenous dihydrotestosterone and albuminuria, glomerulosclerosis, and tubule-interstitial fibrosis progression in castrated male diabetic rats. As men age, a decline in testicular production of testosterone are seen, as well as an increase in sex hormone binding globulin, both of which act to decrease bioavailable testosterone. This study provides the first direct human experimental evidence that testosterone directly modulates renal perfusion. Magnesium, glucose, white blood cell count, platelets, thyroid stimulating hormone, and vitamin D metabolite levels were unchanged. Following the injections, the patient’s serum creatinine levels increased from 133 to 211 μmol/l (reference interval, 62–120 μmol/l) and cystatin C increased from 2.5 to 3.5 mg/l (reference interval, 0.27–1.20 mg/l). A good rule of thumb is to aim for 1g/lb of body weight to optimize your protein intake. When your body has more protein being created than broken down, it means you’re in a state of anabolism, or positive nitrogen balance. Besides these mechanisms, other factors including high-protein diet (by increasing the renal blood flow and GFR) and elevated blood pressure (via hypertensive arterionephrosclerosis) may have additive/synergistic adverse effects on glomeruli . Among all seven patients with long-term follow-ups, discontinuation of anabolic steroids, along with the use of RAAS blockers and/or corticosteroids, has led to the improvement or stabilization of serum creatinine, weight loss, and proteinuria reduction. Administration of 0.75 mg/day dihydrotestosterone (low dose) had nephroprotective effects; whereas, administration of 2.0 mg/day dihydrotestosterone (high dose) accelerated renal injury process. Furthermore, a study on orchidectomized adult male Sprague-Dawley rats demonstrated that a subcutaneous injection of testosterone for 7 days with a dose of 125 mg/kg/day or 250 mg/kg/day can increase water re-absorption. Conversely, exogenous testosterone administration can also cause renal dysfunction, renal injury progression, and proteinuria . The authors attributed AKI in the bodybuilders to the combination effects of excess creatine and protein with steroid injections along with hypervitaminosis D and phosphate nephropathy . The topic on testosterone and ApoA1 values in training are not sufficiently presented, hence there is still a necessity for more thorough research. In hypogonadal men, after enhancing testosterone level, in this case one month of supplementation treatment with a dose of 100 mg, the researchers observed a decrease in ApoA1, alongside a decrease in HDL cholesterol and an increase in hepatic lipase activity . Based on many previously published papers there is a strong association with testosterone levels and ApoA1 values.