Worn out? Irritable? Gaining weight? Low libido? Memory problems? You and your doctor might not think about low testosterone when you think about your symptoms, but you might after reading this.
Many symptoms of low testosterone are similar to those of other conditions. Before you self-diagnose with Dr. Google or get a prescription based only on how you feel, see if low testosterone might be the issue.
- How Common is Low Testosterone?
- Why Are So Few Aware of the Low Testosterone Problem?
- Signs and Symptoms of Low Testosterone
- What Does Testosterone Do?
- What Lowers Testosterone?
- How Can You Increase Testosterone?
- Supplements, HCG, and Hormone Therapy
- Managing Estrogen
- Is testosterone therapy bad?
- Should teens or young adults use testosterone-boosting supplements?
- Wrapping it Up
How Common is Low Testosterone?
Some experts believe a quarter of 30-year-old men have low testosterone.
The situation is slightly better for women. In his book, Unleash the Power of the Female Brain, Daniel Amen, MD, points out that 20 percent of women have low testosterone. He also suggests another 20 percent of women have polycystic ovary syndrome (PCOS), which is caused by testosterone levels that are too high.
Unfortunately, these numbers are based on people who have gone to the doctor and are experiencing symptoms. Chances are, many more men and women have testosterone levels out of balance. If you haven’t had your testosterone levels checked, you could be among them.
Why Are So Few Aware of the Low Testosterone Problem?
Most people don’t know how important testosterone is. They see it as a hormone for making muscles and boosting libido.
They don’t relate testosterone to heart disease, insulin resistance, degenerative brain disease, or depression. As you’ll see, low testosterone plays a role in these conditions and many more.
It’s for this reason I recommend adults, beginning at age 30, get a complete lab panel each year. If everyone did this, they’d likely identify trends leading to health problems, long before they became actual “health problems.”
These trends include changes in hormones like testosterone. Fortunately, you don’t have to wait for your doctor to order such a lab panel (most doctors won’t). You can order your own, like the Hormone Health panel from Life Time.
Signs and Symptoms of Low Testosterone
Healthcare practitioners diagnose men as “low” in testosterone when their levels fall below 300ng/dL. However, signs and symptoms of low testosterone often occur at levels much higher.
The “normal” range for men is 300ng/dL to 1,100ng/dL. That’s an enormous range! It’s like saying someone from Dallas lives near the Mexican border: They might live in the state next to Mexico, but it’s still 878 miles to the border. It’s not close at all.
A testosterone level of 400 ng/dL is far from optimal, even though it’s in the “state” of normal.
As far back as the 1970s, some endocrinologist actually knew the proper optimized range of total testosterone (800 to 1200ng/dL).Dr. Dan Purser, Improving Male Sexuality, Fertility and Testosterone
Here we are, decades later, and the optimal range is rarely discussed. Many doctors don’t know of this “optimal” range. As a result, a doctor tells a guy he’s normal as long as his levels are above 300 ng/dl.
Identifying low testosterone in women is even more of a challenge. Their “normal” range is 15 to 70ng/dL. Because normal levels are so much lower in women, doctors often overlook the importance of measuring it.
Though their total levels are much lower, they still have a broad range in what’s considered “normal.” A woman can feel entirely different at a concentration of 15ng/dL versus 65ng/dL, even though she’d be considered normal in both circumstances.
The following two tables outline common signs and symptoms of low testosterone.
|Signs and Symptoms of Low Testosterone in Men|
|Increased “central” body fat (“pot” belly)||Irritability and anxiety||Hot flashes|
|Gynecomastia||Sleep disturbances||Poor memory|
|Osteoporotic fracture||Fatigue||Lack of morning erections|
|Loss of height||Muscle aches||Decreased ejaculate volume|
|Loss of facial, axillary and pubic hair||Decreased strength||Infertility|
|Testicular atrophy||Reduced libido||Poor memory|
|Signs and Symptoms of Low Testosterone in Women|
|Gain in body fat||Reduced sex drive or sexual function||Loss of muscle or muscle weakness|
|Fatigue||Hot flashes||Menstrual irregularity or absence|
|Diminished exercise performance||Fatigue||Bone loss|
|Loss of height||Muscle aches||Infertility|
Low testosterone can cause cardiovascular disease, type 2 diabetes, loss of muscle, low bone density, reduced physical performance, decreased libido, depression, and cognitive decline.
In a study of almost 400 men under 50 years old who had low testosterone, one-third had low bone density. That’s a lot of men with a condition historically seen in women.
Low testosterone might also cause cognitive dysfunction, including the development of Alzheimer’s disease.
What Does Testosterone Do?
What doesn’t testosterone do? The following are some of the highlights.
Testosterone plays an important role in maintaining muscle mass in men and women. When you have more muscle, you not only move better, you also maintain healthier blood-sugar levels. It can help you look better, too.
As testosterone rises, so do levels of hemoglobin. Increasing testosterone can improve your ability to circulate oxygen throughout your body. Increasing testosterone levels may also resolve cases of anemia.
Insulin Resistance and Diabetes
Since muscle is the primary storage area of glucose, muscle loss contributes to insulin resistance, which can develop into type 2 diabetes.
If you have low testosterone, you are much more likely to develop type 2 diabetes in the next five years, even if you have no signs of diabetes today.
Testosterone is necessary for proper bone metabolism. Ten to 20 percent of men have osteoporosis, and low testosterone may be the leading cause.
Confidence and Mood
Low testosterone contributes to symptoms of depression. Sometimes people describe themselves as lacking ambition, drive, or passion.
At the other end of the extreme in testosterone levels, you find people with a desire to dominate others, with more aggressive behavior. While extreme levels of testosterone can cause someone to act like a jerk, optimal levels help you keep your head up and confidently ask for what you want in life.
The confidence-boosting effect is seen in women and men alike.
Researchers treated women with Social Anxiety Disorder (SAD) with a single dose of testosterone. A hallmark sign of SAD is “gaze avoidance” — they have trouble looking others in the eye. Following the testosterone treatment, the women with SAD had no trouble holding the gaze of someone else, suggesting their confidence went up and anxiety went down.
Cognitive Function and Emotional Control
In older men, those with higher testosterone have better memory and spatial awareness and display better strategic thinking. They also have better emotional control and reactions.
Women treated with testosterone also experience improvements in memory and spatial awareness.
If you’re a guy, and you cry more than you used to, or you tend to overreact to situations, your testosterone and estrogen might be out of balance.
Libido and Sexual Function
I can’t talk about the importance of testosterone and not speak of libido and sexual function. Higher testosterone levels almost always equal greater desire, interest, and pleasure in sex for both men and women.
For women, low libido is more often tied to depression or her emotional state. However, women with low testosterone often have low libido and rarely think about sex. They also deal with sexual dysfunction, such as dryness and discomfort during intercourse.
With about one in five married couples in a “sexless marriage,” low testosterone may be one of many causes.
What Lowers Testosterone?
The following are some of the major causes of low testosterone.
Overweight and Obesity
Low testosterone can increase body-fat levels, and increased body fat can lower testosterone. Together, they can create a vicious cycle of continued body-fat gain and reduced testosterone. Testosterone therapy decreases body fat and increases lean mass (muscle tissue).
Women are the most susceptible to stress-related drops in testosterone. In women, the adrenal glands contribute directly to testosterone production by producing testosterone itself, or hormone precursors, like DHEA.
Since the adrenal glands also produce the stress hormone cortisol, excessive physical or psychological stress in women can limit their ability to make testosterone.
Chronic stress can also reduce testosterone levels in men, but it often requires a lot more stress, or a more extended period of enduring it.
Sleep debt, or interrupted sleep, has been shown to lower testosterone and elevate cortisol levels.
A staggering 26 percent of middle-aged men have obstructive sleep apnea (OSA), which drastically limits testosterone production.
Testosterone is secreted in pulses during the 24-hour cycle. Your highest production takes place in the morning, so disrupted or insufficient sleep limits it.
Moderate-to-heavy alcohol consumption decreases testosterone. If you self-medicate with alcohol because of excessive stress and then sacrifice sleep because of your drinking, you create a triple-whammy on your testosterone production.
Rosuvastatin, which is sold under the label Crestor, was shown to suppress testosterone levels during a six-month study. Fortunately, testosterone levels climbed back up after discontinuing use.
Atorvastain (Lipitor) is also known to lower testosterone levels. The findings of one study recommended combining Lipitor and testosterone therapy, as patients had better outcomes than when using Lipitor alone.
The better question, though, is whether the Lipitor is appropriate for men in the first place. After all, elevated cholesterol is not necessarily a problem of its own, but rather a symptom of something else.
Head Trauma (Men)
Head trauma can damage the pituitary, which is what tells the testes to produce testosterone (pituitary damage in women affects estrogen production).
In some, the effects of head trauma are short-term, lasting days to weeks; others may not experience effects until years later. And still, in others, head trauma causes an immediate effect that never goes away. Doctors often overlook the pituitary as the cause of low testosterone in men.
Oral Contraceptives (Women)
Women using oral contraceptives often have lower testosterone levels, which is ironic. The contraceptive that’s used to prevent pregnancy can lead to low testosterone’s lack of libido, making sex less likely anyway.
Long-term Calorie Restriction
Calorie-restriction is a significant stress on the body. When you don’t provide enough nutrition, testosterone production declines. Excessive exercise, without sufficient nutrition does the same thing.
And you don’t have to be on a 500-calorie diet to see your testosterone plummet. You just have to continually under-nourish your body compared to the energy you expend.
Corticosteroids such as prednisone and cortisone can lower testosterone levels. If you use these medications on a daily basis, get your testosterone levels checked.
How Can You Increase Testosterone?
In men, the testes produce testosterone directly. The pituitary gland stimulates the hypothalamus, which stimulates the testes.
In women, it’s more complicated. For pre-menopausal women, a quarter of testosterone is produced by the ovaries, and another quarter is produced by the adrenal glands. The other half of testosterone is produced from hormone precursors, including androstenedione (the prohormone Mark McGwire allegedly used), and dehydroepiandrosterone (DHEA).
Androstenedione is banned and no longer available as a dietary supplement. DHEA is available as a dietary supplement, and is often recommended for women, to support optimal testosterone production.*
In my experience, it’s best to do everything you can with your lifestyle, exercise, nutrition, and supplementation. Then, if you still need help, hormone therapy can be an appropriate and safe way to optimize levels.
In many studies, higher vitamin D is significantly associated with higher testosterone, although other smaller studies did not find this association. Vitamin D plays a role in many areas of metabolism, so supplementing with it is a must even if you have optimal testosterone levels already.
According to a study, on evenings when couples had sex, their testosterone levels increased. On evenings when they didn’t, testosterone levels fell. If you need another good reason to make love to your spouse, there you go.
Another study found that for women who were not on hormonal contraceptives, just thinking sexual thoughts increased testosterone. Those on contraceptives did not experience the testosterone boost.
It’s also believed that a woman’s psychological state can affect testosterone. When she feels sexy, her testosterone levels go up.
Eat animal-based protein, which is a good source of saturated and monounsaturated fats. It also contains cholesterol, which can be used by the body to make testosterone.
Because of its resveratrol content, a single drink of red wine can increase testosterone levels. Be careful though: More than a serving of alcohol can reduce it.
One study showed resistance training increased testosterone levels by 30 percent. Another study showed hypertrophy-style training increased levels 136 percent, while strongman-style training increased testosterone 74 percent.
Resistance training increases testosterone for a short period, during and after exercise. But by exercising five to six days a week, week-after-week, the long-term effects can be significant over time.
Sufficient, quality sleep is one of the most influential ways to maximize hormone production. Most hormones rely on a healthy circadian rhythm. If you don’t get enough sleep, or you go to sleep at inconsistent times, you’ll disrupt your circadian rhythm and sabotage your body’s hormone production.
Supplements, HCG, and Hormone Therapy
While I’ve included a long list of references for this article — and there are many more I’ve reviewed but didn’t include — there is far more anecdotal evidence than published human studies.
Many of the herbs below have been used for hundreds, if not thousands of years. And contrary to what the media would have you believe, dietary supplements have a solid safety record.
I left the history lessons out of this article, but if you’re into history or geography, you might be fascinated to learn where many of the plants come from and how they’ve been used in traditional medicine.
Most of our knowledge of natural therapies has been passed down through generations. It’s the result of experimentation. Even today, we can learn a lot from our own experiments.
The Foundational Five
As we explain in the article on The Foundational Five, don’t waste time and money on targeted supplements if you don’t have a solid foundation with the Foundational Five first. Shorting yourself on those micronutrients not only affects your overall health, but can also directly or indirectly affect testosterone.
Tribulus terrestris is also known as Gokshur, Gokharu, and puncture vine. Both men and women seem to benefit from tribulus terrestris. Although this article is about testosterone, I felt it was valuable to highlight some of the other benefits of tribulus terrestris.
Tribulus terrestris contains saponins, which increase luteinizing hormone (LH), testosterone, estrogen, and other hormones. Other constituents increase DHEA, which can convert to testosterone.
Supplementing with tribulus improved sexual desire, vaginal lubrication, and arousal. Women with hypoactive sexual desire disorder who took 750mg/day of tribulus terrestris experienced improved sexual desire and elevated testosterone levels. Women with elevated blood sugar experienced lower glucose levels following supplementation.*
An animal study showed tribulus terrestris reduced symptoms of depression.* Depression and testosterone levels are often related, possibly because the depressed feelings contribute to reduced testosterone, or because the lower testosterone increases feelings of depression. It’s also possible that depression stems from a disruption in the hypothalamus, which also affects testosterone levels.
In animal studies, tribulus terrestris prevented increases in total cholesterol and triglycerides in animals with normal levels and lowered total cholesterol, LDL, and triglycerides in those with elevated levels.*
Other studies on animals showed that tribulus terrestris supports healthy brain function, protects the liver, helps maintain normal inflammatory levels, dulls pain, and may protect cells from the development of cancer.*
In a study of rugby players, the addition of tribulus terrestris to a training program did not enhance muscle mass or strength more than the training program alone. However, in a study of men with low testosterone levels, a dose of 250mg, three times per day, did improve testosterone levels and erectile function.*
Ashwagandha (also known as Withania somnifera, Indian Ginseng, and Winter Cherry) is an adaptogenic herb that has been shown to support healthy blood pressure, stimulate thyroid function, maintain normal cortisol levels, and support optimal testosterone levels.*
In a double-blind, placebo-controlled study of exercising men, supplementation with ashwagandha significantly increased testosterone levels compared with the placebo group. Muscle strength and size was greater, body-fat percentage improved more, and muscle recovery were also enhanced in the supplemented group compared to the control group.
Ashwagandha supplementation increased testosterone levels in infertile men. Like tribulus, ashwagandha has also been shown to improve sexual function and interest in women. Whether it’s a result of increased testosterone, reduced stress levels, or something else, remains to be determined.
Others Herbs and Extracts to Consider
Fenugreek (also known as Trigonella foenum-graecum) is another adaptogen that seems to support optimal testosterone levels, possibly by helping to modulate cortisol levels. As with tribulus, fenugreek also seems to support those with symptoms of polycystic ovary syndrome (PCOS).
Longjack root, or Tongkat Ali, grows in Malaysia, Indonesia, and Vietnam. Evidence suggests it supports optimal testosterone levels in both men and women.
To avoid making a book out of this article, let me just suggest some other herbs and extracts that have good anecdotal evidence, even if scientific research hasn’t yet supported them: Horny Goat Weed (epimedium), Maca, Holy Basil, Coleus forskohlii, Cordyceps, and Velvet Antler.
Lower vitamin D levels are also associated with low testosterone.
Other micronutrients, including vitamin C, boron, conjugated linoleic acid, and magnesium might also play a role in testosterone production.
This underscores the importance of supplementing with a high-quality multivitamin.
In some people, the issue with their hormones is not that testosterone is too low: It’s that estrogen is too high.
In men, excess estrogen can lead to gynecomastia, a decrease in facial hair, and other feminine characteristics. In women, excess estrogen can lead to “estrogen dominance.”
Though they are not necessarily “testosterone-enhancing,” aromatase-inhibitors block the conversion of testosterone to estrogen, leaving more testosterone available as testosterone. With less estrogen, testosterone has a more powerful effect. Other supplements enhance the removal of estrogens from the body.
Indole-3-carbinol (I3C), and Diindolylmethane (DIM) — found in cruciferous vegetables — help to support normal estrogen levels. I3C is a precursor of DIM, and there is a lot of debate about which one is better. In my opinion, it’s just trial and error to see which works better for you.
One of the easiest and cheapest ways to help normalize estrogen levels is to eat more fiber. Fiber binds to estrogens in the intestines and helps remove them from the body.
Is testosterone therapy bad?
I’m dead-set on doing whatever you can to naturally support optimal health, including your hormones. However, these changes may not be sufficient for some people to achieve optimal testosterone levels.
In my opinion, you’re better off using a prescription and feeling your best, than feeling lousy and remaining “all natural.”
I have to repeat, though: Don’t just go with pharmaceuticals because it sounds easier than taking care of your health naturally.
The two most common medical options are human chorionic gonadotropin (HCG) and exogenous testosterone.
HCG stimulates the production of testosterone, just as luteinizing hormone does. Exogenous testosterone bypasses the body’s job in producing testosterone, and you get it into your body on your own.
Should teens or young adults use testosterone-boosting supplements?
Most sports performance supplement consumers are high-school and college-aged young adults.
While there are a lot of kids today who are unhealthy and display symptoms of low testosterone and/or excessive estrogen, this is most often the result of their lifestyle and nutrition choices. Introducing testosterone-boosting supplements would be a waste of money.
For young adults who are healthy and fit, I wouldn’t expect them to see much of a difference from using these supplements. Their bodies are at their hormonal peak. Young adults can maximize what their bodies are meant to do without using testosterone-boosters.
I wouldn’t mess with testosterone-boosting supplements until reaching an age where hormone levels start to decline (usually around age 30).
Wrapping it Up
Don’t suffer from the symptoms of low testosterone. Life is more fun and exciting when your testosterone levels are optimal. And your attitude may be a lot better, too, which others will appreciate.
There’s so much you can do to maintain optimal levels at any age, but remember: You don’t have to take all of this on at once.
Start with your nutrition and lifestyle choices. Then get in the habit of strength training three to four times per week. And while you make these longer-term changes, experiment with some of these nutritional supplement options above.
Adaikan PG, Gauthaman K, Prasad RN, Ng SC. Proerectile pharmacological effects of Tribulus terrestris extract on the rabbit corpus cavernosum. Ann Acad Med Singapore. 2000;29(1):22–26
Ahmad MK, Mahdi AA, Sukla KK, et al. Withania somnifera improves semen quality by regulating reproductive hormone levels and antioxidative stress in seminal plasma of infertile males. Fertility and Sterility. 2010;94(3):989-996
Araujo AB, Travison TG, Leder BZ, McKinlay JB. Correlations between serum testosterone, estradiol, and sex hormone-binding globulin and bone mineral density in a diverse sample of men. J Clin Endocrinol Metab. 2008;93:2135–41.
Atlantis E, Fahey P, Martin S, et al. Predictive value of serum testosterone for type 2 diabetes risk in men. BMC Endocrine Disorders. 2016;16:26
Balin J. The many faces of testosterone. Clin Interv Aging. 2007;2(4):567-576
Bao Y, Johansen KL. Diagnosis and treatment of low testosterone among patients with end-stage renal disease. Semin Dial. 2014
Cangemi R, Friedmann AJ, Holloszy JO, Fontana L. Long-term effects of calorie restriction on serum sex-hormone concentrations. Aging Cell. 2010;9(2):236-242
Cha JS, Park JK. The relationship between serum total testosterone and free testosterone levels with serum hemoglobin and hematocrit levels: a study in 1221 men. Aging Male. 2016;19(4):290-214
Chhatre S, Nesari T, Somani G, Kanchan D, Sathaye S. Phytopharmacological overview of Tribulus terrestris. Phamacon Rev. 2014;8(15):45-51
Chin KY, Ima-Nirwana S, Wan Ngah WZ. Vitamin D is significantly associated with total testosterone and sex hormone-binding globulin in Malaysian men. Aging Male. 2015;18(3):175-179
Chu S, Qu W, Pang X, Sun B, Huang X. Effect of saponin from Tribulus terrestris on hyperlipidemia. Zhong Yao Cai. 2003;26:341–4. [PubMed: 14535016]
Dandona P, Rosenberg MT. A practical guide to male hypogonadism in the primary care setting. Int J Clin Pract. 2010;64(6):682-696
Dabbs JM, Mohammed S. Male and female salivary testosterone concentrations before and after sexual activity. Physiol Behav. 1992;52(1):195-197
de Souza KZ, Vale FB, Gerber S. Efficacy of Tribulus terrestris for the treatment of hypoactive sexual desire disorder in postmenopausal women: a randomized, double-blinded, placebo-controlled trial. Menopause. 2016;23(11):1252-1256
Dongre S, Langade D, Bhattacharyya S. Efficacy and Safety of Ashwagandah (Withania somnifera) Root Extract in Improving Sexual Function in Women: A Pilot Study. Bio Med Res. Int. 2015. http://dx.doi.org/10.1155/2015/284154
Enter D, Terburg D, Harrweijn A, Spinhoven P, Roelofs K. Single dose testosterone administration alleviates gaze avoidance in women with Social Anxiety Disorder. Psychoneuroendocrinology. 2016;63:26-33
Estley CJ, Amdur RL, Irwig MS. High Rates of Depression and Depressive Symptoms among Men Referred for Borderline Testosterone Levels. J Sex Med. 2015;12(8):1753-60
Gauthaman K, Ganesan AP. The hormonal effects of Tribulus terrestris and its role in the management of male erectile dysfunction—an evaluation using primates, rabbit and rat. Phytomedicine 2008;15(1–2):44–54
Ghiciuc CM, Dima-Cozma LC, Bercea RM, et al. Imbalance in the diurnal salivary testosterone/cortisol ratio in men with severe obstructive sleep apnea: an observational study. Braz J Otorhinolaryngol. 2016;82(5):529:535
Goldey KL, van Anders SM. Sexy thoughts: Effects of sexual cognitions on testosterone, cortisol, and arousal in women. Res on Sex Arous. 2011;59(5):754-764
Guay A, Davis SR. Testosterone insufficiency in women: fact or fiction? Excerpt from World Urology 2002. 20:106-110
Gunnels TA, Bloomer RJ. Increasing Circulating Testosterone: Impact of Herbal Dietary Supplements. J Plant Biochem & Physiol. 2:130 doi:10.4172/2329-9029.1000130
Haffner SM, Karhapää P, Mykkänen L, Laakso M. Insulin resistance, body fat distribution, and sex hormones in men. Diabetes 1994;43:212-9
Hassan J, Barkin J. Testosterone deficiency syndrome: benefits, risks, and realities associated with testosterone replacement therapy. Can J Urol. 2016;23(Suppl 1):20-30
Heijboer AC, Oosterwerff M, Schroten NF, et al. Vitamin D supplementation and testosterone concentrations in male human subjects. Clin Endocrinol. 2015;83(1):105-110
Hisasue S. Contemporary perspective and management of testosterone deficiency: Modifiable factors and variable management. Int J Urology. 2015;22:1084-1095
Hsieh CJ, Huang B. Rosuvastatin decreases testosterone levels but not sexual function in men with type 2 diabetes. Diabetes Res Clin Pract. 2016;120:8-88
Kacker R, Conners W, Zade J, Morgentaler A. Bone mineral density and response to treatment in men younger than 50 years with testosterone deficiency and sexual dysfunction or infertility. J Urol. 2014;19(4):1072-1076
Krysiak R, Gilowski W, Okopie?. The effect of testosterone on cardiometabolic risk factors in atorvastatin-treated men with late-onset hypogonadism. Pharmacol Rep. 2016;68(1):196-200
Leão L, Duarte M, Farias ML. Female Androgen Insufficiency and Potential Risks of Therapeutic Replacement. Arg Bras Endocinol Metab. 2005;49:205-216
Lu W, Du N, Liu Y, et al. Low Testosterone Level and Risk of Alzheimer’s Disease in Elderly Men: a Systematic Review and Meta-Analysis. Mol Neurobiol. 2016;53(4):2679-84
Mayo Medical Laboratories. Mayo Clinic. Testosterone, Total, Bioavailable, and Free, Serum. http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/83686
Michnovicz JJ, Bradlow HL. Induction of Estradiol Metabolism by Dietary Indole-3-carbinol in Humans. J Natl Cancer Inst. 1990;82(11):947-949
Moffat SD, Zonderman AB, Metter EJ, et al. Longitudinal assessment of serum free testosterone concentration predicts memory performance and cognitive status in elderly men. J Clin Endocrinol Metab. 2002;87:5001–7.
Mulligan T, Frick MF, Zuraw QC, Stemhagen A, McWhirter C. Prevalence of hypogonadism in males at least 45 years: the HIM Study. Int J Clin Pract. 2006;60(7):762-769.
Nimptsch K, Platz EA, Willett WC, Giovannucci E (2012) Association between plasma 25-OH vitamin D and testosterone levels in men. Clin Endocrinol (Oxf) 2012;77:106-112.
Pope HG, Cohane GH, Kanayama G, et al. Testosterone gel supplementation for men with refractory depression: a randomized, placebo controlled trial. Am J Psychiatry. 2003;160:105–11.
Postigo S, Lima SM, Yamada SS, et al. Assessment of the Effects of Tribulus Terrestris on Sexual Function of Menopausal Women. Rev Bras Ginecol Obstet. 2016;38:140-146
Prasad AS, Mantzoros CS, Beck FW, Hess JW, Brewer GJ. Zinc status and serum testosterone levels of healthy adults. Nutrition 1996;12:344-348.
Raben A., Kiens B, Ritchter EA, Rasmussen LB, Svenstrup B, Micic S, Bennett P. Serum sex hormones and endurance performance after a lacto-ovo vegetarian and a mixed diet. Med. Sci. Sports Exercise. 1992;24:1290–1297
Roaiah MF, El Khayat YI Gamal El Din SF, Abd El Salam MA. Pilot Study on the Effect of Botanical Medicine (Tribulus terrestris) on Serum Testosterone Level and Erectile Function in Aging Males With Partial Androgen Deficiency (PADAM). J Sex Marital Ther. 2016;42(4):297-301
Rogerson S, Riches CJ, Jennings C, et al. The effect of five weeks of Tribulus terrestris supplementation on muscle strength and body composition during preseason training in elite rugby league players. J Strength Cond Res. 2007;21(2):348-53
Samani NB, Jokar A, Soveid M, et al. Efficacy of Tribulus Terrestris Extract on the Serum Glucose and Lipids of Women with Diabetes. Iran J Med Sci. 2016;41(3):S5
Shamloul R. Natural aphrodisiacs. J Sex Med. 2010;7(1 Pt 1):39–49
Shin S, Jeon JH, Park D, Jang MJ. Choi JH. trans-resveratrol relaxes the corpus cavernosum ex vivo and enhances testosterone levels and sperm quality in vivo. Arch Pham Res. 2008;31(1):83-87 Shin YS, You JH,
Sowers MF, Beebe JL, McConnell D, et al. Testosterone Concentrations in Women Aged 25–50 Years: Associations with Lifestyle, Body Composition, and Ovarian Status. Am J Epidemiol. 2001;153:256-264
Sternbach H. Age-associated testosterone decline in men: clinical issues for psychiatry. Am J Psychiatry. 1998;155:1310-1318
Swaroop A, Jaipuriar AS, Gupta SK, et al. Efficacy of a Novel Fenugreek Seed Extract (Trigonella foenum-graecum) in Polycystic Ovary Sundrome (PCOS). Int J Med Sci. 2015;12(10)825-831
Thomson CA, Chow SHH, Doe D, et al. Effect of Diindolylmethane on Estrogen-related Hormones, Metabolites and Tamoxifen Metabolism: Results of a Randomized, Placebo-controlled Trial. J Cancer Epidem Biomar Preven. 2017;26(3) DOI: 10.1158/1055-9965.EPI-17-0027
Traish AM. Testosterone and weight loss: the evidence. Curr Opin Endocrinol Diabetes Obes. 2014;21:313-322
Tuncer MA, Yaymaci B, Sati L, Cayli S, Acar G, Altug T, Demir R. Influence of Tribulus terrestris extract on lipid profile and endothelial structure in developing atherosclerotic lesions in the aorta of rabbits on a high-cholesterol diet. Acta Histochem. 2009;111:488–500. [PubMed: 19269683]
Van den Berghe G. The neuroendocrine response to stress is a dynamic process. Best Pract Res Clin Endocrinol Metab. 2001;15: 405-19.
Volek JS, Kraemer WJ, Bush JA, Incledon T, Boetes M. Testosterone and cortisol in relationship to dietary nutrients and resistance exercise. J Appl Physiol. 1997;82:49-54
Wang Z, Zhang D, Hui S, Zhang Y, Hu S. Effect of tribulus terrestris saponins on behavior and neuroendocrine in chronic mild stress depression rats. J Trandit Chin Med. 2013;33(2):228-232
Wankhede S, Langade D, Joshi K, et al. Examining the effect of Withania somnitera supplementation on muscle strength and recovery: a randomized controlled trial. J of Int Soc of Sports Nutr. 2015;12:43:1-11
Wehr E, Pilz S, Boehm BO, März W, Obermayer-Pietsch B. Association of vitamin D status with serum androgen levels in men. Clin Endocrinol (Oxf) 2010;73:243-248.