Studies on low testosterone, what drives it, when it is real versus a measurement artifact, and what lifts it naturally.
This study looked at whether low testosterone in middle-aged and older men is tied to worse blood vessel health through effects on mitochondria, the tiny power plants inside cells. Researchers…
This study looked at whether time spent outdoors is linked to testosterone in men. It analyzed 2,205 men in the US National Health and Nutrition Examination Survey, tracking daily outdoor…
This study looked at whether vitamin D changes how well metformin (a common diabetes drug that lowers blood sugar) can bring down prolactin (a pituitary hormone that suppresses testosterone when…
This study set out to clarify how testosterone levels change after a single bout of exercise, given conflicting findings in past research. It reviewed 15 randomized controlled trials with 251…
This study built a better way to read testosterone in men, especially men with obesity, by accounting for SHBG (sex hormone-binding globulin, a protein that binds testosterone and sets how…
This study looked at whether a man's TyG index tracks with his risk of low testosterone as he ages. The TyG index is a simple score figured from fasting blood…
This study set out to see whether exposure to bright light is linked to testosterone in men, an area far less studied than diet and exercise. It analyzed data from…
This study tested whether pairing intermittent fasting with weightlifting improves body composition in obese men. It randomly assigned 20 obese men aged 20 to 30 to either a normal diet…
This systematic review set out to assess how GLP-1 receptor agonists (a class of diabetes and weight-loss drugs) affect male reproductive hormones, semen quality, and metabolic health. It pooled data…
This systematic review and meta-analysis set out to see whether vitamin D supplements raise testosterone or related markers in men. It pooled randomized trials measuring total testosterone, SHBG (sex hormone-binding…
This study asked how sex hormones relate to the risk of dying, separately for men and women. It analyzed 7,294 U.S. adults in the National Health and Nutrition Examination Survey…
This study set out to explore how obesity and chronic inflammation relate to testosterone levels in men. It analyzed data from over 7,400 adult men in the US, using body…
This study set out to explore whether cannabis use affects hormone levels in young men. It compared blood steroid levels between 47 cannabis users and 47 non-users, measuring 70 different…
This review looked at how to tailor injectable testosterone therapy for men with confirmed hypogonadism, meaning the testicles do not make enough testosterone, causing symptoms such as low libido, fatigue…
This review looked at how aging affects men's hormones, sleep, and metabolism, centering on two kinds of hypogonadism (when the testicles do not make enough testosterone, causing symptoms like low…
This study looked at how depression, testosterone levels, and shift work are linked in men with symptoms of low testosterone. It reviewed medical records and survey data from 766 men…
This study looked at what drives low testosterone in U.S. men, going beyond aging to include habits and life circumstances. It analyzed over 10,000 men aged 18 and up from…
This review set out to examine how microplastics (tiny plastic particles) affect the male reproductive system at the cellular and molecular level. It compiled findings from multiple studies across scientific…
This study looked at how a man's testosterone and SHBG relate to where his body stores fat. SHBG, or sex hormone-binding globulin, is a protein that binds testosterone and sets…
This study tested whether CoQ10, L-carnitine (an amino-acid-like nutrient the body uses to turn fat into energy), or both together improve semen quality in men with low sperm count, poor…
This is a narrative review (an expert summary of existing research, not a new experiment) asking whether testosterone replacement therapy (TRT) could help men with low testosterone hold onto muscle…
This review gathers recent evidence on what damages male fertility and how much of it can be undone. Smoking raises sperm DNA fragmentation (breaks in the genetic material inside sperm)…
This study asked which workplace exposures matter most for men's reproductive health. It took 80 men working in an automobile parts plant, measured their exposure to magnetic fields, electric fields,…
This study looked at how lifestyle and hormones affect semen quality and sperm DNA health in men. It examined 278 Indian men aged 21 to 50, measuring sperm count, movement,…
This study set out to explore how trace elements in the blood might relate to testosterone levels and symptoms like low energy, mood issues, and sexual health in young men.…
This study looked at whether vitamin D3 supplementation improves hormone levels and semen quality in infertile men. It pooled data from six randomized controlled trials involving 945 men, measuring changes…
This study looked at how diet relates to sperm quality, comparing the Mediterranean diet, which is built on seasonal, fresh and whole foods, against ultra-processed foods, which are high in…
This narrative review looked at the use, benefits, and safety of testosterone replacement therapy (TRT) in men aged 40-49 with low testosterone. It synthesized findings from randomized controlled trials and…
This study looked at whether eating more omega-3 fatty acids (healthy fats found in fish and some plants) is linked to higher testosterone levels in men. It used data from…
This meta-analysis (a study that statistically pools many earlier studies) looked at how body mass index (BMI, a weight-for-height number used to flag over- or under-weight) relates to sperm quality…
This study looked at whether sleep duration affects markers of male fertility in young men. It analyzed 1,055 Danish men who reported their sleep habits and gave semen and blood…
This systematic review and meta-analysis set out to assess whether coenzyme Q10 (CoQ10) supplementation improves semen quality and male hormone levels. It pooled data from eight randomized controlled trials involving…
This study set out to clarify how bisphenol A (BPA, a chemical used in food packaging and container linings) affects men's reproductive health. It pooled 18 studies that measured BPA…
This meta-analysis set out to measure how much testosterone men with obesity get back when they lose weight, comparing low-calorie diets with bariatric surgery. It pooled 44 studies covering 1,774…
This is a narrative review, which means the authors gathered and discussed existing work rather than running a study of their own. It asks whether the damage COVID-19 does to…
This meta-analysis set out to examine how alcohol intake affects male reproductive health by looking at semen quality, antioxidant levels in semen, sperm DNA damage, and sex hormones. It pooled…
This study set out to examine how cigarette smoking affects semen quality, hormone levels, metabolic health, zinc levels, and sperm DNA damage in young Russian men. It compared 450 smokers…
This study set out to test whether ashwagandha, a traditional herb, could reduce stress and fatigue in overweight or mildly obese adults aged 40-75 who reported high stress and fatigue.…
This study set out to see whether testosterone in men varies with the season, independently of age, weight and existing illness. It used the medical records of 27,328 Israeli men…
This study set out to see whether exercise training raises resting testosterone in men who were not very active but otherwise healthy. It pooled 11 randomized trials covering 421 men…
This meta-analysis set out to clarify how sleep deprivation affects testosterone levels in healthy men. It pooled data from 18 studies involving 252 men, comparing testosterone levels after partial sleep…
This study set out to find out whether men actually use scrotal cooling devices as directed, and what happened to their semen results when they did. Forty men attending a…
This study set out to see what happens to a man's testosterone when he cuts fat out of his diet, at a time when levels have been falling across Western…
This study tested whether a specially designed cooling garment could lower scrotal skin temperature during ordinary daily life. Three volunteer urologists wore it, with a cold pack inside that was…
This study set out to compare how young and older men's hormone levels respond to a night without sleep. It measured testosterone, luteinizing hormone (LH, a pituitary hormone that signals…
This study looked at how going without sleep affects muscle recovery after hard exercise. Ten men did 240 hard lengthening contractions of the thigh muscles, then either stayed awake for…
This meta-analysis set out to see whether physical exercise causes a short-term rise in testosterone levels in men. It pooled data from 48 studies that measured total and free testosterone…
This study set out to find which stage of sperm production is most sensitive to mild heat. Five healthy volunteers wore a specially designed underwear that held the testicles up…
This study looked at whether cutting sleep short changes testosterone in healthy young men, across two separate trials. In the first, 14 men had 4 hours in bed for 5…
This study set out to see if men's reproductive hormones follow seasonal patterns, as they do in many animals. It analyzed over 12,000 hormone tests from nearly 7,500 men aged…
This study asked what a mild, sustained rise in testicular temperature does to the chromosomes inside sperm. Five fertile volunteers wore specially designed underwear that held the testicles up against…
This study set out to find hormonal and biochemical markers that could flag overtraining syndrome (OTS) in male athletes. It compared 14 men with OTS to 25 healthy athletes and…
This review looked at the link between obesity and low testosterone in men, focusing on how weight affects hormone levels and what treatments might help. It examined studies on men…
This study set out to test whether vitamin D supplements raise testosterone in healthy men. It randomly assigned 98 men with normal testosterone but low vitamin D to a high…
This study set out to see whether shorter rest periods between sets of resistance exercise boost muscle growth signals more than longer rests. Sixteen young men did leg exercises at…
This study set out to see what repeated heat does to sperm. Twenty men with normal semen results were randomly split into two groups, and both had their testicles warmed…
This study set out to see what sustained scrotal heating does to semen and to the sperm's genetic material in fertile men. Nineteen healthy volunteers wore a warming belt at…
This study looked at what sustained scrotal heating does to semen and to the sperm's genetic material in already fertile men. Twenty-five healthy volunteers wore a warming belt at 40…
This study looked at whether spending time relaxing in a forest (forest therapy) could lower blood pressure and stress in middle-aged men with high-normal blood pressure. Men walked and did…
This review gathers what is known about why heat harms sperm production, and how. It sets out the things that raise testicular temperature, from the surroundings a man is in…
This study looked at whether catching up on sleep at the weekend improves insulin sensitivity and hormones in men who habitually sleep too little in the week. Nineteen such men…
This study looked at whether vitamin D levels track with testosterone, and with hypogonadism (when the testicles do not make enough testosterone, which shows up as low drive, fatigue and…
This review set out to gather what is known about whether cooling the scrotum helps sperm production. The authors searched two large medical databases, EMBASE from 1980 to 2010 and…
This study set out to see how losing weight affects testosterone in men with obesity. It pooled 24 trials comparing low-calorie diets against bariatric surgery, measuring changes in total testosterone…
This study set out to test whether spending a short time in a forest has measurable health benefits compared to staying in a city. Twenty healthy young men were split…
This study set out to see how cutting sleep affects glucose handling and hormones in young men. Fourteen healthy men were kept in a laboratory for two nights of 10…
This study tested ways to prevent scrotal overheating in men using laptop computers. Twenty-nine healthy men had their scrotal temperature measured during three one-hour sessions: sitting with legs close together,…
This study looked at whether magnesium supplements raise testosterone in athletes and in sedentary men, at rest and after exercising to exhaustion. Thirty healthy men aged 18 to 22 were…
It has been suggested that cycling warms the testicles as a ride goes on, and that this in turn harms semen quality. This study tested the first half of that…
This review looked at how heat stress on the testicles affects semen quality in men. It examined studies on factors like prolonged sitting, tight underwear, sauna use, and fever, and…
This study set out to measure whether testosterone in American men had fallen over calendar time, separately from the fall that comes with getting older. It drew 2769 measurements from…
This study reviewed how the scrotum's role in keeping the testicles cooler than core body temperature affects sperm production. It looked at evidence from men with conditions like undescended testicles…
This study looked at whether cooling the scrotum overnight improves semen quality in men with a history of undescended testicles and a low sperm count, a group with few options…
This study set out to measure how much using a laptop on your lap raises scrotal temperature, a known risk factor for male infertility. Researchers measured scrotal temperature in 29…
This study asked why men differ so much in how warm their testicles run. Scrotal skin temperature was logged every five minutes for 24 hours in 48 men, made up…
This study set out to find which parts of an ordinary day actually move scrotal temperature. A thermistor (a small temperature sensor) was clipped to the underwear of 101 men…
This study set out to track how testosterone changes as men age, and whether the change is aging itself or the illnesses and medications that come with it. It measured…
This study looked at whether reducing genital heat could improve semen quality in men with a poor sperm count, poor movement and abnormal shape. It compared those men against men…
This study asked whether the ordinary, everyday variation in scrotal temperature is enough to matter for sperm. Sixty men from a group of couples planning their first pregnancy wore a…
This study set out to test whether driving a car for long stretches raises scrotal temperature, a known risk factor for sperm health. Nine men had their scrotal temperature measured…
This lecture is the field's own summary of why the testicles sit outside the body and what happens when they get warm. It sets out the evidence that the testes…
This study looked at whether zinc levels affect testosterone in healthy men. It compared zinc levels and testosterone in 40 men aged 20 to 80, induced zinc deficiency in 4…
This study looked at whether cooling the testicles every day helps men whose couples had been unable to conceive. It followed 64 men who had subfertile semen and a raised…
This study set out to test whether cooling the scrotum could improve semen in men with a low sperm count or poor sperm movement. Fifty such men wore jockey shorts…
This study looked at whether cooling the scrotum could improve semen quality in men whose infertility came with a raised testicular temperature. Six men with poor semen results and a…