The Ultimate in Male Performance
Lay people and medical professionals alike are well acquainted with the importance of GH in our bodies. Studies have shown that having higher levels of GH can increase lean body mass, reduce fat, increase muscle strength, and improve aerobic endurance . If people desire to increase GH naturally without synthetic injections, they can do so by increasing their intensity of training of the large muscle groups. But all that training needs to be fueled with the right GH precursors to achieve optimal levels. Take an ice machine as an example. The rate of ice cube production depends on how fast the machine is churning and the abundant supply of the precursor – water. No matter how well the machine is churning, if the water supply is low, the ice cube production will slow down. Similarly, our body has the most intricate and complicated pathways to churn out the appropriate levels of the vital hormones for human thriving, but we need to feed the hormonal pathways with the right concoction of hormonal precursors for the optimal production. Force was especially formulated for just that reason.
So what are those important precursors and adjunct supplements for optimal hormonal balance? Force contains the potent key stimulatory amino acids – such as L-Arginine and L-Glycine – to encourage growth hormone release. These have been shown to increase fat burning, while building muscle [2,3,4]. Vitamin B6 also has been shown to increase GH and decrease prolactin production . The downregulation of prolactin means an increase in testosterone levels. We have combined the raw ingredients necessary for optimization of the body’s hormones such as GH and testosterone. We have combined micronutrients like Zinc, Magnesium and vitamin B6 to fuel the hormonal pathways synergistically [6,7,8,9].
Our product goes beyond the basic micronutrients, however. We pooled together everything in the current literature about other ingredients that can optimize human performance. Studies have shown that our patented KSM-66 Ashwaganda can assist in regulation of serum testosterone, can improve exercise endurance, and also increase muscle strength [10,11] Tongkat Ali and Fadogia Agrestis have been mentioned often in the airwaves and the podcasts because of their potential to increase testosterone levels in healthy and hypogonadal men, by triggering luteinizing hormone. [13,14] Tribulus Terrestris is one of the original testosterone supporters, and recent studies have shown that it can boost testosterone, when combined with exercise . Any product that enhances testosterone not only affects performance in the gym but also in the bedroom. The third leg of the formula starts with Muira Puama which is indigenous to Brazil and supports healthy sexual function and vigor.  Epimedium, also known as horny goat weed, has a main chemical compound named Icariin that has been shown to have similar effects as some prescription erectile dysfunction medications. 
All these various ingredients work in synergy together to help increase testosterone, increase muscle mass, assist with libido, decrease stress hormones, and ultimately build the best you. Force is built to enhance your current active lifestyle. We start with micronutrients and multiple different herbs for both testosterone and GH support. These, in turn, will assist with exercise in the gym and the bedroom and will increase muscle mass, which can increase GH and testosterone. Let the Force be the fuel source that catapults your fitness journey to the next level.
An Unfortunate New Normal
The son surpassing the father is a storyline that goes back at least as far as Greek and Roman mythology. The story of Cronus, who feared being usurped by his children, and Oedipus, the son who succeeded, are two popular tales that fit the storyline. Most fathers want better for their children, and many children want to achieve more than their parents. However, when it comes to our biology and our hormone levels, the younger generation does not have it better.
In the last 20 years alone, the number of young men who meet the criteria of having clinically low testosterone levels [<300ng/dL] have increased 5-fold in the last 20 years (Lokeshwar et al., 2021). The prevalence of low testosterone increased from 4% in 1999-2000 to 20% in 2015-2016. That’s not just suboptimal – that’s a medical phenomenon. On top of that, even those within the normal range are experiencing a decline; in the same time comparison, average testosterone levels decreased over 25% from 605 to 451ng/dL. And that’s in young men – older men have it even worse.
Men aged 67 years old in 2006-2009 had a total testosterone level of 473ng/dL, but in 2016-2019, just ten years later, an average 67 year old man only had a level of 343ng/dL, a 27% decline (Chodick et al., 2020). Data collected in the late 1970’s show that sixty-seven year old men born in the 1910s had a testosterone level even greater thanyoung men today; it was 632ng/dL (Perheentupa et al., 2013).
It's not just testosterone. Male fertility is on the decline too. Average sperm count in adult men decreased by 50% over 50 years from the 1960s to 2010s (Sengupta et al., 2018). Likewise, birth rate per capita for the year 2021 was 12 – half of what it was 70 years earlier in 1951 (United Nations, 2022). As you can easily imagine, cultural differences made it unlikely they talked about erectile dysfunction, but from the little data that is published on the topic, that shows the same trend – doubling over the past 30 years (Porst & Sharlip, n.d.). Gruesome.
Why? What Can We Do About It?
For perspective, the generational changes described are not age-related changes. However, age does play a huge role. Studies that have followed the same men over time have reported that total testosterone decreases at a rate of about 1.5% every year, and bioavailable testosterone decreases even faster – by as much as 3% per year (Jones, 2008). We can’t stop aging, but we can work to slow both age-related changes and those due to this other phenomenon.
Some of the generational changes can be explained by lifestyle. Fatter men have lower testosterone levels, and we’re fatter now than we’ve ever been (Lokeshwar et al., 2021). Soy proteins contain phytoestrogens, which decrease testosterone in men (Goodin et al., 2007). There are also xenoestrogens in other products, like plastics, which used to contain the notorious BpA, but still contain other phthalates that can reduce testosterone (Cariati et al., 2019). Beer, stress, pesticides, lack of sleep and more are all things that affect our endocrine system, and the list goes on. On the flip side, resistance training increases testosterone and growth hormone (Craig et al., 1989). Eating more saturated fat increases testosterone and the testosterone response to exercise, as testosterone is made from cholesterol (Volek et al., 1997).
There are also several other nutritional strategies we can employ once we understand our hypothalamic pituitary adrenal and testicular axis, and a few other things, a little better.
The Male Endocrine System
Humans are a complicated biological system, and it doesn’t get any simpler when it comes to hormone regulation and the complexities of our reproductive and sexual health. With testosterone taking center stage for so many critical functions, let’s start there.
Testosterone is made from cholesterol via a few other compounds you may or may not have heard of, such as pregnenolone, dehydroepiandrosterone (DHEA), and androstenedione. The final products of that metabolic pathway are actually estradiol (estrogen), which is made when testosterone encounters the enzyme, aromatase, or dihydrotestosterone (DHT), when encountering 5-alpha reductase. Now, DHT isn’t all that bad, it can make your hair fall out if you are genetically predisposed to male-pattern baldness, but otherwise it’s pretty androgenic, giving you nice secondary sex characteristics – a manlier man. Estrogen, on the other hand, is mixed bag, believe it or not.
If you have more testosterone, you will have more estrogen, and that’s not a bad thing. Estrogen actually can contribute to muscle growth (Parr et al., 2014b). The problem is when there is too much estrogen compared to the levels of testosterone where men lose traditional testosterone-related function, such as being lean and ready for action. When estrogen is high and testosterone is low, we have even worse of a problem than it seems because estrogen tells the man’s body to slow testosterone production. It thinks that testosterone is high since estrogen is made from testosterone. These two hormones operate via binding to their respective receptors – testosterone to the androgen receptor and estrogen to the estrogen receptor. Just like having more testosterone, having more androgen receptor helps add lean muscle.
To make more of either, we need to look at the hypothalamic pituitary testicular axis, or HPTA. Testosterone is made in the testes via StAR protein, which are stimulated by luteinizing hormone (LH) and follicle stimulating hormone (FSH) to make testosterone and sperm. LH and FSH come from the pituitary, which is stimulated by gonadotropin releasing hormone (GnRH) from the hypothalamus. Thus, if one can trigger the hypothalamus and/or pituitary to increase LH and FSH, the testes will produce testosterone. And many of the intermediate steps that can be enhanced along the way will also support the production of more testosterone, as often times, this heavily regulated, redundant system can counteract the effects of just one augmentation alone.
Beyond testosterone, although it certainly plays its own role, men, especially aging men, today are also challenged with declining sexual and reproductive health. If there is one thing we know in both medical and pop culture circles, it is that Viagra works. Viagra works by inhibiting phosphodiesterase (PDE) 5 to increase blood flow to the penis, specifically to the corpus cavernosum of the penis. Reproductive health (seminal health), for simplicity’s sake, goes hand in hand with testosterone production – if you increase LH and FSH, the semen is healthier.
Almost entirely independent from testosterone from a metabolic perspective is one that goes hand-in-hand, growth hormone. While the name does ring true, GH is actually better for losing fat than it is for building muscle. In one six month study, scientists observed a 10% increase in muscle mass, but participants lost 16% of their adipose tissue (Lee Vance, 1990). Not unlike testosterone, GH decreses over 30% from their peak levels in those over age 55 (HO et al., 1987).
For body composition purposes, growth hormone balances out cortisol. Both help release glucose and fat from storage, but cortisol frees amino acids from muscle proteins while GH helps drive amino acids into the muscle to contribute to a positive nitrogen balance. While they have similar function, the two are generally not active at the same time. Cortisol will suppress GH, which like testosterone, has its release aided by the hypothalamus.
FORCE Testosterone and HGH Support
FORCE was engineered to aid all of the known pathways towards enhanced testosterone, growth hormone, and male functioning. Different environmental and societal pressures have driven down testosterone levels in men of all ages, and men over 45 are in even more dire need of endocrine support. Using targeted micronutrients, traditional Ayurvedic and Chinese medicine, and cutting-edge ecdysteroids, FORCE helps increase testosterone and growth hormone while supporting a more youthful feeling man.
Micronutrients – Vitamin B6, Chelated Magnesium, Chelated Zinc
We are little without good nutrition. When it comes to the male endocrine system, the key vitamins and minerals are vitamin B6, Magnesium, and Zinc. When vitamin B6 is low, testosterone production is decreased even though LH can be normal (part of that redundant system) (Symes et al., 1984). B6 has also been shown to increase GH and decrease prolactin (Delitala et al., 1976). As prolactin negatively regulates testosterone, this is a second mechanism by which proper B6 levels can help maintain healthy testosterone levels.
Magnesium and Zinc are others that support both testosterone and GH. We already know that exercise can increase testosterone, and when exercising while supplementing magnesium, testosterone levels increase even more (Cinar et al., 2011). When zinc levels are low, the testes cannot convert cholesterol to testosterone (Lei et al., 1976). When zinc levels are normal, zinc supplementation can still increase testosterone levels (Kaya et al., 2006). When used together, these micronutrients have been able to increase testosterone by 33% (Brilla & Conte, 2000).
Fadogia agrestis is also known as Black Aphrodisiac, and one of the reasons it works is because it contains alkylamide glycosides – something unique within the hormone support space. These functional constituents increase cholesterol inside the testes. This herb has been found to quickly increase testosterone – taking just 5 days for a significant increase (Yakubu et al., 2005). Black Aphrodisiac can also help with erectile dysfunction, but unlike others that help with ED, Fadogia agrestis may actually help men last longer.
Tribulus terrestris is one of the originals in testosterone support. Featured in Ayurveda and traditional Chinese medicine, saponins from Tribulus are one of the only known herbs that can increase androgen receptor content (Gauthaman & Adaikan, 2005). Men supplementing with Tribulus have reported enhanced libido, satisfaction, and improvements in symptoms of ED (Leisegang & Finelli, 2021).
Otherwise known as Potency Wood, Muira puama is an Amazonian herb that has helped men improve their erectile function in as little as 2 weeks (Shamloul, 2010). Centuries of use in the region have earned it the modern title, “Viagra of the Amazon.”
Maca is a South American medicine used since 3800 B.C. that improves aphrodisia, but is not mediated by hormones, such as testosterone, like most supplements that are effective for arousal. The active components of Maca are known as Macamides. These molecules help with the stress and depression some men experience when feeling pressured to perform and reduce erectile dysfunction (Brooks et al., 2008; Rubio et al., 2006; Zenico et al., 2009).
Epimedium is also known as Horny Goat Weed; according to the legend, a Chinese goat herder was once puzzled as to why sometimes his animals would engage in incessant sexual activity. There are a few options when it comes to herbals for ED, but none are stronger than the active contained in Epimedium, Icariin. Icariin is a PDE-5 inhibitor with 100x stronger affinity for PDE-5 than any other enzymes (Xin et al., 2003). It’s nearly unheard of for a dietary supplement to compare to prescription medication, but icariin has a potency 50% the strength of Viagra (Zhang et al., 2012).
Tongkat Ali, Eurycoma longfolia or Longjack for short, is an herb coming from southeast Asia. Like epimedium, longjack also helps increase blood flow to the corpus cavernosum, but it does so by a mechanism complementary to PDE-5 (Chiou & Wu, 2012). In other words, longjack is complimentary to and synergistic with epimedium and PDE-5 inhibitors. Studies have also shown longjack to delay ejaculation (Chiou & Wu, 2012), increase LH (Pratomo, 2017), improve sperm count over 65% (Tambi & Imran, 2010), and increase muscle mass (Hamzah & Yusof, 2003).
Cnidium is a plant native to China, not to be confused with brain-booster, bacopa monnieri. Traditional use is as a libido enhancer, and modern evidence indicates the same – supplementation increases frequency of sex (Dau et al., 2020). Cnidium may also increase NO, helping with erectile function (Chen et al., 2000), but most importantly, it can improve the rate limiting step in testicular testosterone synthesis by increase StAR protein activity (Pan et al., 2015).
Ecdysteroids – Ecdysterone & Turkesterone
Ecdysteroids are a class of steroid hormones found usually in insects, but also in some plants. Ecdysterone works by antagonizing estrogen receptors. It has been noted to robustly increase protein synthesis in muscle cells (Parr et al., 2014a), and this has led to increased gains in muscle mass (Isenmann et al., 2019).
Turkesterone is the most anabolic of the ecdysteroid class of supplements. It increased growth by 63.5% compared to 51.9% with Ecdysterone and less than 25% with all other ecdysteroids (Syrov, 2000). In addition to muscle growth and enhanced response to resistance training, turkesterone is also erythropoietic, meaning it can increase red blood cell regeneration, which may enhance oxygen carrying capacity and endurance (Syrov et al., 1997).
Amino Acids – Arginine & Glycine
Arginine and glycine are the two most critical amino acids for growth hormone formation. Arginine supplementation can be anabolic, and when it is, knockout model research has shown the hypothalamus, which controls GH release, to be required for arginine to exert anabolic effects. Ingestion of both glycine and arginine in isolation produce robust increases in GH – glycine boosts GH over 3x over 3 hours, and arginine can increase it over 100% with larger doses (and a nice 35% with small doses) (Collier et al., 2005; Kasai et al., 1978; Zajac et al., 2010).
FORCE Your Testosterone Up
We are all in control of our own destiny. Societal, environmental, and generational pressures are driving our natural testosterone and growth hormone levels dramatically lower, negatively impacting our ability to be the man we can be. FORCE was developed to help you reclaim your maximum potential, grow up strong in the eyes of your father regardless of your age, and reinvigorate you in your pursuit of happiness. Get FORCE today!
- Fred R. Sattler and others, Testosterone and Growth Hormone Improve Body Composition and Muscle Performance in Older Men, The Journal of Clinical Endocrinology & Metabolism, Volume 94, Issue 6, 1 June 2009, Pages 1991–2001, https://doi.org/10.1210/jc.2008-2338
- Pahlavani N, Entezari MH, Nasiri M, Miri A, Rezaie M, Bagheri-Bidakhavidi M, Sadeghi O. The effect of l-arginine supplementation on body composition and performance in male athletes: a double-blinded randomized clinical trial. Eur J Clin Nutr. 2017 Apr;71(4):544-548. doi: 10.1038/ejcn.2016.266. Epub 2017 Jan 25. Erratum in: Eur J Clin Nutr. 2017 Aug;71(8):1028. PMID: 28120856.
- Kanaley JA. Growth hormone, arginine and exercise. Curr Opin Clin Nutr Metab Care. 2008 Jan;11(1):50-4. doi: 10.1097/MCO.0b013e3282f2b0ad. PMID: 18090659.
- Kasai K, Suzuki H, Nakamura T, Shiina H, Shimoda SI. Glycine stimulated growth hormone release in man. Acta Endocrinol (Copenh). 1980 Mar;93(3):283-6. doi: 10.1530/acta.0.0930283. PMID: 7376793.
- Manore MM. Vitamin B6 and exercise. Int J Sport Nutr. 1994 Jun;4(2):89-103. doi: 10.1123/ijsn.4.2.89. PMID: 8054964.
- Prasad AS, Mantzoros CS, Beck FW, Hess JW, Brewer GJ. Zinc status and serum testosterone levels of healthy adults. Nutrition. 1996 May;12(5):344-8. doi: 10.1016/s0899-9007(96)80058-x. PMID: 8875519.
- Te L, Liu J, Ma J, Wang S. Correlation between serum zinc and testosterone: A systematic review. J Trace Elem Med Biol. 2023 Mar;76:127124. doi: 10.1016/j.jtemb.2022.127124. Epub 2022 Dec 23. PMID: 36577241.
- Cinar V, Polat Y, Baltaci AK, Mogulkoc R. Effects of magnesium supplementation on testosterone levels of athletes and sedentary subjects at rest and after exhaustion. Biol Trace Elem Res. 2011 Apr;140(1):18-23. doi: 10.1007/s12011-010-8676-3. Epub 2010 Mar 30. PMID: 20352370.
- Maggio M, De Vita F, Lauretani F, Nouvenne A, Meschi T, Ticinesi A, Dominguez LJ, Barbagallo M, Dall'aglio E, Ceda GP. The Interplay between Magnesium and Testosterone in Modulating Physical Function in Men. Int J Endocrinol. 2014;2014:525249. doi: 10.1155/2014/525249. Epub 2014 Mar 3. PMID: 24723948; PMCID: PMC3958794.
- Clinical Evaluation of the Spermatogenic Activity of the Root Extract of Ashwagandha (Withania somnifera) in Oligospermic Males: A Pilot Study Ambiye, V. R., Langade, D., Dongre, S., Aptikar, P., Kulkarni, M., & Dongre, A. (2013). Evidence-Based Complementary and Alternative Medicine, 2013.
- Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial Wankhede, S., Langade, D., Joshi, K., Sinha, S. R., & Bhattacharyya, S. (2015). Journal of the International Society of Sports Nutrition, 12(1), 43.
- Rudman D, Feller AG, Nagraj HS, Gergans GA, Lalitha PY, Goldberg AF, Schlenker RA, Cohn L, Rudman IW, Mattson DE. Effects of human growth hormone in men over 60 years old. N Engl J Med. 1990 Jul 5;323(1):1-6. doi: 10.1056/NEJM199007053230101. PMID: 2355952.
- Pratomo, H. (2017). Eurycoma longifolia extract increases intracellular production activity of luteinizing hormone (LH) in pituitary. 030112. https://doi.org/10.1063/1.4991216
Brilla, L. R., & Conte, V. (2000). Effects of a novel zinc-magnesium formulation on hormones and strength. Journal of Exercise Physiology Online, 3(4), 26–36.
Brooks, N. A., Wilcox, G., Walker, K. Z., Ashton, J. F., Cox, M. B., & Stojanovska, L. (2008). Beneficial effects of Lepidium meyenii (Maca) on psychological symptoms and measures of sexual dysfunction in postmenopausal women are not related to estrogen or androgen content. Menopause (New York, N.Y.), 15(6), 1157–1162. https://doi.org/10.1097/gme.0b013e3181732953
Cariati, F., D’Uonno, N., Borrillo, F., Iervolino, S., Galdiero, G., & Tomaiuolo, R. (2019). “Bisphenol a: an emerging threat to male fertility.” Reproductive Biology and Endocrinology, 17(1), 6. https://doi.org/10.1186/s12958-018-0447-6
Chen, J., Chiou, W. F., Chen, C. C., & Chen, C. F. (2000). Effect of the plant-extract osthole on the relaxation of rabbit corpus cavernosum tissue in vitro. The Journal of Urology, 163(6), 1975–1980. http://www.ncbi.nlm.nih.gov/pubmed/10799242
Chiou, W.-F., & Wu, T.-S. (2012). 9-hydroxycanthin-6-one induces penile erection and delays ejaculation. The Journal of Sexual Medicine, 9(4), 1027–1036. https://doi.org/10.1111/j.1743-6109.2011.02296.x
Chodick, G., Epstein, S., & Shalev, V. (2020). Secular trends in testosterone- findings from a large state-mandate care provider. Reproductive Biology and Endocrinology, 18(1), 19. https://doi.org/10.1186/s12958-020-00575-2
Cinar, V., Polat, Y., Baltaci, A. K., & Mogulkoc, R. (2011). Effects of magnesium supplementation on testosterone levels of athletes and sedentary subjects at rest and after exhaustion. Biological Trace Element Research, 140(1), 18–23. https://doi.org/10.1007/s12011-010-8676-3
Collier, S. R., Casey, D. P., & Kanaley, J. A. (2005). Growth hormone responses to varying doses of oral arginine. Growth Hormone and IGF Research, 15(2), 136–139. https://doi.org/10.1016/j.ghir.2004.12.004
Craig, B. W., Brown, R., & Everhart, J. (1989). Effects of progressive resistance training on growth hormone and testosterone levels in young and elderly subjects. Mechanisms of Ageing and Development, 49(2), 159–169. https://doi.org/10.1016/0047-6374(89)90099-7
Dau, T. D., Le, M. H., Nguyen, T. T. G. H., Dang, T. N. M., Do, T. N. Q., & Tran, Q. T. (2020). Effects of Cnidium monnieri (L.) Cuss. fruit extract on sexual behaviors in male rats. Clinical Phytoscience, 6(1), 80. https://doi.org/10.1186/s40816-020-00227-3
Delitala, G., Masala, A., Alagna, S., & Devilla, L. (1976). Effect of pyridoxine on human hypophyseal trophic hormone release: a possible stimulation of hypothalamic dopaminergic pathway. The Journal of Clinical Endocrinology and Metabolism, 42(3), 603–606. https://doi.org/10.1210/jcem-42-3-603
Gauthaman, K., & Adaikan, P. G. (2005). Effect of Tribulus terrestris on nicotinamide adenine dinucleotide phosphate-diaphorase activity and androgen receptors in rat brain. Journal of Ethnopharmacology, 96(1–2), 127–132. https://doi.org/10.1016/j.jep.2004.08.030
Goodin, S., Shen, F., Shih, W. J., Dave, N., Kane, M. P., Medina, P., Lambert, G. H., Aisner, J., Gallo, M., & DiPaola, R. S. (2007). Clinical and Biological Activity of Soy Protein Powder Supplementation in Healthy Male Volunteers. Cancer Epidemiology, Biomarkers & Prevention, 16(4), 829–833. https://doi.org/10.1158/1055-9965.EPI-06-0882
Hamzah, S., & Yusof, A. (2003). The Ergogenic Effects of Eurycoma Longifolia Jack: A Pilot Study. British Journal of Sports Medicine, 37(5), 464–470. https://doi.org/10.1136/bjsm.37.5.464
HO, K. Y., EVANS, W. S., BLIZZARD, R. M., VELDHUIS, J. D., MERRIAM, G. R., SAMOJLIK, E., FURLANETTO, R., ROGOL, A. D., KAISER, D. L., & THORNER, M. O. (1987). Effects of Sex and Age on the 24-Hour Profile of Growth Hormone Secretion in Man: Importance of Endogenous Estradiol Concentrations*. The Journal of Clinical Endocrinology & Metabolism, 64(1), 51–58. https://doi.org/10.1210/jcem-64-1-51
Isenmann, E., Ambrosio, G., Joseph, J. F., Mazzarino, M., de la Torre, X., Zimmer, P., Kazlauskas, R., Goebel, C., Botrè, F., Diel, P., & Parr, M. K. (2019). Ecdysteroids as non-conventional anabolic agent: performance enhancement by ecdysterone supplementation in humans. Archives of Toxicology, 93(7), 1807–1816. https://doi.org/10.1007/s00204-019-02490-x
Jones, H. (2008). Testosterone for the aging male; current evidence and recommended practice. Clinical Interventions in Aging, Volume 3, 25–44. https://doi.org/10.2147/CIA.S190
Kasai, K., Kobayashi, M., & Shimoda, S. I. (1978). Stimulatory effect of glycine on human growth hormone secretion. Metabolism: Clinical and Experimental, 27(2), 201–208. https://doi.org/10.1016/0026-0495(78)90165-8
Kaya, O., Gokdemir, K., Kilic, M., & Baltaci, A. K. (2006). Zinc supplementation in rats subjected to acute swimming exercise: Its effect on testosterone levels and relation with lactate. Neuro Endocrinology Letters, 27(1–2), 267–270. http://www.ncbi.nlm.nih.gov/pubmed/16648790
Lee Vance, M. (1990). Growth Hormone for the Elderly? New England Journal of Medicine, 323(1), 52–54. https://doi.org/10.1056/NEJM199007053230109
Lei, K. Y., Abbasi, A., & Prasad, A. S. (1976). Function of pituitary-gonadal axis in zinc-deficient rats. The American Journal of Physiology, 230(6), 1730–1732. https://doi.org/10.1152/ajplegacy.1918.104.22.1680
Leisegang, K., & Finelli, R. (2021). Alternative medicine and herbal remedies in the treatment of erectile dysfunction: A systematic review. Arab Journal of Urology, 19(3), 323–339. https://doi.org/10.1080/2090598X.2021.1926753
Lokeshwar, S. D., Patel, P., Fantus, R. J., Halpern, J., Chang, C., Kargi, A. Y., & Ramasamy, R. (2021). Decline in Serum Testosterone Levels Among Adolescent and Young Adult Men in the USA. European Urology Focus, 7(4), 886–889. https://doi.org/10.1016/j.euf.2020.02.006
Pan, Z., Fang, Z., Lu, W., Liu, X., & Zhang, Y. (2015). Osthole, a coumadin analog from Cnidium monnieri (L.) Cusson, stimulates corticosterone secretion by increasing steroidogenic enzyme expression in mouse Y1 adrenocortical tumor cells. Journal of Ethnopharmacology, 175, 456–462. https://doi.org/10.1016/j.jep.2015.10.009
Parr, M. K., Zhao, P., Haupt, O., Ngueu, S. T., Hengevoss, J., Fritzemeier, K. H., Piechotta, M., Schlörer, N., Muhn, P., Zheng, W.-Y., Xie, M.-Y., & Diel, P. (2014a). Estrogen receptor beta is involved in skeletal muscle hypertrophy induced by the phytoecdysteroid ecdysterone. Molecular Nutrition & Food Research, 58(9), 1861–1872. https://doi.org/10.1002/mnfr.201300806
Parr, M. K., Zhao, P., Haupt, O., Ngueu, S. T., Hengevoss, J., Fritzemeier, K. H., Piechotta, M., Schlörer, N., Muhn, P., Zheng, W.-Y., Xie, M.-Y., & Diel, P. (2014b). Estrogen receptor beta is involved in skeletal muscle hypertrophy induced by the phytoecdysteroid ecdysterone. Molecular Nutrition & Food Research, 58(9), 1861–1872. https://doi.org/10.1002/mnfr.201300806
Perheentupa, A., Mäkinen, J., Laatikainen, T., Vierula, M., Skakkebaek, N. E., Andersson, A.-M., & Toppari, J. (2013). A cohort effect on serum testosterone levels in Finnish men. European Journal of Endocrinology, 168(2), 227–233. https://doi.org/10.1530/EJE-12-0288
Porst, H., & Sharlip, I. D. (n.d.). History and Epidemiology of Male Sexual Dysfunction. In Standard Practice in Sexual Medicine (pp. 43–48). Blackwell Publishing Ltd. https://doi.org/10.1002/9780470755235.ch4
Pratomo, H. (2017). Eurycoma longifolia extract increases intracellular production activity of luteinizing hormone (LH) in pituitary. 030112. https://doi.org/10.1063/1.4991216
Rubio, J., Caldas, M., Dávila, S., Gasco, M., & Gonzales, G. F. (2006). Effect of three different cultivars of Lepidium meyenii (Maca) on learning and depression in ovariectomized mice. BMC Complementary and Alternative Medicine, 6(1), 23. https://doi.org/10.1186/1472-6882-6-23
Sengupta, P., Borges, E., Dutta, S., & Krajewska-Kulak, E. (2018). Decline in sperm count in European men during the past 50 years. Human & Experimental Toxicology, 37(3), 247–255. https://doi.org/10.1177/0960327117703690
Shamloul, R. (2010). Natural Aphrodisiacs. The Journal of Sexual Medicine, 7(1), 39–49. https://doi.org/10.1111/j.1743-6109.2009.01521.x
Symes, E. K., Bender, D. A., Bowden, J. F., & Coulson, W. F. (1984). Increased target tissue uptake of, and sensitivity to, testosterone in the vitamin B6 deficient rat. Journal of Steroid Biochemistry, 20(5), 1089–1093. https://doi.org/10.1016/0022-4731(84)90348-0
Syrov, V. N. (2000). Comparative experimental investigation of the anabolic activity of phytoecdysteroids and steranabols. Pharmaceutical Chemistry Journal, 34(4), 193–197. https://doi.org/10.1007/BF02524596
Syrov, V. N., Nasyrova, S. S., & Khushbaktova, Z. A. (1997). [The results of experimental study of phytoecdysteroids as erythropoiesis stimulators in laboratory animals]. Eksperimental’naia i Klinicheskaia Farmakologiia, 60(3), 41–44. http://www.ncbi.nlm.nih.gov/pubmed/9324397
Tambi, M. I. B. M., & Imran, M. K. (2010). Eurycoma longifolia Jack in managing idiopathic male infertility. Asian Journal of Andrology, 12(3), 376–380. https://doi.org/10.1038/aja.2010.7
United Nations. (2022). World Population Prospects. https://population.un.org/wpp/
Volek, J. S., Kraemer, W. J., Bush, J. A., Incledon, T., & Boetes, M. (1997). Testosterone and cortisol in relationship to dietary nutrients and resistance exercise. Journal of Applied Physiology, 82(1), 49–54. https://doi.org/10.1152/jappl.1922.214.171.124
Xin, Z. C., Kim, E. K., Lin, C. S., Liu, W. J., Tian, L., Yuan, Y. M., & Fu, J. (2003). Effects of icariin on cGMP-specific PDE5 and cAMP-specific PDE4 activities. Asian Journal of Andrology, 5(1), 15–18. http://www.ncbi.nlm.nih.gov/pubmed/12646997
Yakubu, M. T., Akanji, M. A., & Oladiji, A. T. (2005). Aphrodisiac potentials of the aqueous extract of Fadogia agrestis (Schweinf. Ex Hiern) stem in male albino rats. Asian Journal of Andrology, 7(4), 399–404. https://doi.org/10.1111/j.1745-7262.2005.00052.x
Zajac, A., Poprzecki, S., Zebrowska, A., Chalimoniuk, M., & Langfort, J. (2010). Arginine and ornithine supplementation increases growth hormone and insulin-like growth factor-1 serum levels after heavy-resistance exercise in strength-trained athletes. Journal of Strength and Conditioning Research, 24(4), 1082–1090. https://doi.org/10.1519/JSC.0b013e3181d321ff
Zenico, T., Cicero, A. F. G., Valmorri, L., Mercuriali, M., & Bercovich, E. (2009). Subjective effects of Lepidium meyenii (Maca) extract on well-being and sexual performances in patients with mild erectile dysfunction: a randomised, double-blind clinical trial. Andrologia, 41(2), 95–99. https://doi.org/10.1111/j.1439-0272.2008.00892.x
Zhang, J., Wang, Y.-B., Ma, C.-G., Liu, T., Li, W.-R., Gong, Y.-Q., & Xin, Z.-C. (2012). Icarisid II, a PDE5 inhibitor from Epimedium wanshanense, increases cellular cGMP by enhancing NOS in diabetic ED rats corpus cavernosum tissue. Andrologia, 44 Suppl 1, 87–93. https://doi.org/10.1111/j.1439-0272.2010.01144.x