Total physical activity was defined as the total number of MET hours/week (Ainsworth et al., 2011). Activity levels were converted to metabolic equivalent (MET) scores, with 8.0 MET for one minute of vigorous activity and 4.0 MET for one minute of moderate or transported physical activity. Data on total energy, protein, carbohydrate, fiber, and fat intakes were collected through a 24-hour dietary recall interview. Systemic pathologies such as diabetes mellitus and CKD impair Leydig cell function through oxidative stress and inflammatory pathways, ultimately causing hypogonadism (Leisegang et al., 2021). In contrast to testosterone, DHEA and DHEA sulfate have been found to act as high-affinity agonists of these receptors. The areas of binding are called hormone response elements (HREs), and influence transcriptional activity of certain genes, producing the androgen effects. 5α-DHT binds to the same androgen receptor even more strongly than testosterone, so that its androgenic potency is about 5 times that of T. Free testosterone (T) is transported into the cytoplasm of target tissue cells, where it can bind to the androgen receptor, or can be reduced to 5α-dihydrotestosterone (5α-DHT) by the cytoplasmic enzyme 5α-reductase. Androgens such as testosterone have also been found to bind to and activate membrane androgen receptors. For adult females, testosterone enhances libido. Levels of testosterone are naturally much higher in males. Your adrenal glands also produce the hormone dehydroepiandrosterone (DHEA), which your body transforms into testosterone and estrogen. If testosterone levels are too high or too low, it can cause certain symptoms. Testosterone levels are naturally much higher in males. First, controlling estradiol levels is easier the less body fat you have. Calculating it is quite easy, despite the fact that different units are often used to measure testosterone and estradiol levels. Two of the immediate metabolites of testosterone, 5α-DHT and estradiol, are biologically important and can be formed both in the liver and in extrahepatic tissues. It is bound 65% to sex hormone-binding globulin (SHBG) and 33% bound weakly to albumin. Finally, increasing levels of testosterone through a negative feedback loop act on the hypothalamus and pituitary to inhibit the release of GnRH and FSH/LH, respectively. The male generative glands also contain Sertoli cells, which require testosterone for spermatogenesis. Testosterone is also synthesized in far smaller total quantities in women by the adrenal glands, thecal cells of the ovaries, and, during pregnancy, by the placenta. In the bones, estradiol accelerates ossification of cartilage into bone, leading to closure of the epiphyses and conclusion of growth. The bones and the brain are two important tissues in humans where the primary effect of testosterone is by way of aromatization to estradiol. In measurements of testosterone in blood samples, different assay techniques can yield different results. 5α-Reductase is highly expressed in the male reproductive organs (including the prostate gland, seminal vesicles, and epididymides), skin, hair follicles, and brain and aromatase is highly expressed in adipose tissue, bone, and the brain. Certain cytochrome P450 enzymes such as CYP2C9 and CYP2C19 can also oxidize testosterone at the C17 position to form androstenedione. In addition to 6β- and 16β-hydroxytestosterone, 1β-, 2α/β-, 11β-, and 15β-hydroxytestosterone are also formed as minor metabolites. For women, testosterone is produced in smaller amounts but is essential for bone strength and sexual interest. It helps in the development of male physical features like body and facial hair, deeper voice, and muscle strength. Additionally, testosterone influences mood, energy levels, and overall physical and mental health. However in females, there is no significant correlation between testosterone and body composition. Conversely, males displayed higher A/G ratio, lean mass percentage (LMP), arm circumference, and waist circumference as opposed to females. Additionally, testosterone decreased by 0.21 ng/dL for every 1% increase in LMP.Furthermore, we conducted an analysis on the population with a BMI ≥ 30, which is classified as obese, and observed consistent findings with those reported earlier in males. For every 1% increase in APF, testosterone increased by 0.15ng/dL, and for every 1% increase in GPF, testosterone levels decreased by 0.15 ng/dL. Specifically, when TPF increased by 1%, testosterone levels increased by 0.19 ng/dL. Regular exercise, especially resistance training, has been shown to potentiate muscle hypertrophy and increase testosterone levels (Vingren et al., 2010). A recent double-blind randomized controlled trial (RCT) reported modest but significant improvements in muscle mass and strength after 3 years of testosterone administration in older men with low-to-normal testosterone levels (Hildreth et al., 2013). Serum testosterone levels also decline by ∼110 ng/dL per decade in older adults (Morley et al., 1997), prompting interest in their interplay with muscle health.
