This article attempts to review some of the myths and misconceptions of testosterone enhancing substances as well as estrogen balancers and blockers. Primarily it looks at various testosterone pro-hormones, including their methods of delivery, as well as known neuroendocrine methods of action and plant extracts.
Phytoandrogen (Prohormone) Formulas
Abstract: Use Of 4-Androstenediol To Increase Testosterone Levels In Humans
The steroid hormone testosterone is considered to be the male virilizing hormone. Its effects include maintenance of muscle and bone mass, sexual function, and psychological well-being among others. As males grow older, especially after the age of 35, a slow decline in testosterone levels is observed which is accompanied by symptoms that have been associated with the condition known as “andropause.” Symptoms of andropause include lethargy, depression, lack of sexual desire and function, and loss of muscle mass and strength.
There are several pharmaceutical methods to restore testosterone levels in humans with sub-optimal levels. Many of these have certain disadvantages however. Testosterone esters in oil depot form have been used as injections for decades, however these injections can be inconvenient and often painful. These depot injections also result in inconsistent blood levels as a supraphysiological surge is seen soon after injection but by the time the next injection is due the levels have often dropped down below standard physiological levels. This is in contrast with testosterone levels under normal conditions, which are quite stable within mild release pulses of approximately 90 minutes duration.
Supraphysiological surges that are seen with injectable preparations may increase the incidence of undesirable side effects (i.e. prostate hypertrophy) as well as cause an amplified shutdown of the hypothalamic/pituitary testicular axis (HPTA). Other pharmaceutical methods for androgen replacement therapy include synthetic oral androgen derivatives. These compounds (i.e. methyltestosterone and fluoxymesterone) are altered in the 17alpha position of the steroid molecule with an alkyl group. This alkyl group renders the steroid impervious to oxidation of the 17beta hydroxyl group in the liver and therefore greatly improves its oral bioavailability compared to the non-alkylated steroids. However this structural modification also has been associated with a greatly increased risk of hepatotoxicity. Therefore these synthetic compounds are far from an ideal solution.
US patent 5578588 discloses a method of increasing testosterone levels in humans by administration of a testosterone precursor, namely androstenedione. Modes of administration discussed include peroral and intranasal.
The pharmacokinetics of such an administration of a precursor is such, that a peak in blood levels is seen at approximately 90 minutes with a subsequent decline to baseline within 3 hours. This fact permits one to more closely simulate the natural endogenous pulsatile release of testosterone through multiple daily dosing of a precursor. This should result in a more normal physiological response with a minimization of side effects and HPTA shutdown. Furthermore, since these precursors are natural steroid hormones found in the blood, and are not 17alpha alkylated compounds, the hepatotoxicity is minimal.
In the course of our research however, we have come to find that the blood testosterone increases seen with oral administration of androstenedione are far less and more variable than what is claimed in US 5578588. It was then the intention of the inventors of this patent, to discover another naturally occurring testosterone precursor that provided a greater blood testosterone level response than androstenedione, but retained all the advantages of being a non-toxic, natural, and quickly metabolizable precursor. This would therefore permit oral administration at a reasonable dose providing a dependable therapeutic response.
The chemical term 4-androstenediol refers to two isomers; 4-androstene-3beta,17beta-diol and 4-androstene-3alpha,17beta-diol. This invention concerns primarily the former isomer. Henceforth the term 4-androstenediol will refer to 4-androstene-3beta,17beta-diol. 4-androstenediol is a naturally occurring compound. It has been identified as a metabolite of testosterone in placental, uterine, testicular, adrenal, and hypothalamic/pituitary tissues. It acts as a very effective precursor to testosterone. 4-androstenediol converts to testosterone via the 3beta-hydroxysteroid dehydrogenase enzyme.
F. Ungar, M. Gut, and R. Dorfman (J. Biol. Chem., 224, 191-200) found that after 4-androstenediol was incubated in liver tissue it metabolized very readily to testosterone.
Blaquier, J., Forchielli, E., and Dorfman, R. (Acta Endocrinologica, 55, 697-704) also revealed that the in vitro conversion of tritiated 4-androstene-3beta,17beta-diol to testosterone in whole human blood was very efficient (15.76%) and was in fact considerably more efficient than titrated androstenedione (5.61%).
After learning of the in-vitro efficacy of 4-androstenediol in regards to testosterone conversion, it was then the intention of the inventors to investigate whether 4-androstenediol would act as an effective in-vivo peroral testosterone precursor in man. It was also the intention of the inventors to investigate whether or not 4-androstenediol would act as a superior peroral testosterone precursor to androstenedione.
A clinical study was therefore undertaken. Seven adult male subjects were used. Each subject was on separate occasions given an oral dose of 100mg. placebo, 4-androstenediol, or androstenedione. Blood samples were collected at 0, 30, 60 and 90 minutes following ingestion and analyzed for total testosterone (TT) and free testosterone (FT) using enzyme-linked immunosorbent assay. Relative to placebo, androstenedione ingestion caused a 14.8% increase in TT and a 10.9% increase in FT at 90 minutes. 4-androstenediol ingestion caused greater responses, producing a 47.7% increase in TT and a 42.5% increase in FT at 90 minutes.
Oral 4-androstenediol can be given in daily doses of 25mg. to 500mg.; preferably 100mg to 300mg. These daily doses can be divided into several subdoses with 3-5 being most preferable. In addition to peroral administration, 4-androstenediol can also be effectively administered by several other routes including transdermal, rectal (suppository), intranasal, and sublingual. A particular advantageous method of sublingual administration involves complexing 4-androstenediol with beta-hydroxypropyl-beta-cyclodextrin which is then pressed into tablets. 4-androstenediol can also be effectively combined with androstenedione to produce a product that contains two precursors that convert to testosterone through two distinct enzyme systems.
- A method of increasing the testosterone levels in humans that involves the administration of an effective amount of 4-androstenediol.
- The method according to claim 1) wherein the mode of administration is peroral and the effective daily dose is 25mg. to 500mg., preferably 100mg to 300mg.
Phytoandrogen Delivery Systems
The Downfall of Oral Ingestion of (Pro)Hormones
While it is reasonable to assume that the oral route for hormones is less optimal because stomach acid destroys the hormone during digestion, this is not true. Steroid hormones such as DHEA, androstenedione, and androstenediol, are quite stable during digestion and are absorbed fairly well. The problem lies in the fact that before they enter the blood stream where they can be converted into testosterone, they are metabolized in the liver by the so-called “first pass effect of liver metabolism.”
When swallowed, active prohormones are dispersed in the stomach, travel to the small intestine and then go directly to the liver which deactivate more than 95% of the active prohormones. The rapid absorption can also overload enzyme capacity and reduce active testosterone conversion. The same problem exists for oral prescription steroids.
When they enter the liver they are quickly metabolized and rapidly absorbed. In order to avoid this rapid deactivation, chemists alkylated the 17th carbon, forcing the liver to cleave the side chain before dispersion. In a sense this made them time released. But this greater demand on the liver increases liver enzymes and can lead to liver toxicity.
To produce (nor)testosterone from (nor)androstenedione, the body cleaves the double bond at carbon 17 and adds an hydrogen to stabilize the valence. If there isn’t enough enzyme left to convert the (nor)dione it will then release CP450 aromatase to convert it into (nor)estrogen. Similarly if there is not enough of the 3 beta enzyme for the (nor)androstenediol it will secrete 17 keto enzymes to convert to (nor)DHEA which then must wait until more 3 beta enzyme is available.
Studies at Quest Diagnostic Laboratory by researcher Dr. Victor Uralets
These show that the rapid oral absorption of oral prohormones cause abnormal physiological levels of steroid metabolites.
“…Oral administration of androstenedione and/or androstenediol have a devastating effect on the entire steroid profile, immediately increasing concentrations of testosterone, androsterone and etiocholanalone and other endogenous steroids by 100 times. Concentrations of testosterone rises faster than that of epitestosterone, which causes the T/E ratios to exceed 6/1… In sharp contrasts to the sharp shifts of testosterone concentrations from orally administered androstenedione and androstenediol, regular injectable testosterone esters (which are prescription) provide constant concentration of active free testosterone in the blood, which is actually safer and more efficient. As a result, these so called “supplements” are actually more damaging to the body than illegal steroids. In addition, the oral route of administration deactivates most of the dose converting it to useless metabolites, which unnecessarily impact the liver. We do not know how damaging it may be for chronic users…”
Topical Phytoandrogen Formulas (Pro-Vigor ®, Pro-Revitalize ®)
Used for decades in Europe, topical application is the preferred method of delivering hormones into the body. In recent years, medical researchers have realized that many nutrients are more effectively delivered via the skin (the body’s largest organ) than by oral means. When applied topically, hormones are most effectively delivered via the skin because they go straight to the cells where they are needed.
Topical application absorbs more than 90% of most hormones compared to less than 5% when taken orally (Ref. University of Dublin, College of Pharmacology).
By using the skin as a natural reservoir to deliver a continuous flow of hormones into the body, topically applied prohormones offer the following benefits to users when compared to swallowed prohormone capsules.
Because it is applied to the skin and not swallowed, the first pass effect of the liver is bypassed. This reduces waste that occurs with oral products and allows for more efficient conversion of the testosterone precursors. A greater effect at a lower, safer dose is the end result. This means that a higher percentage of these androgen precursors can be converted into the parent hormone (testosterone) using a much lower dose than is needed when taken by mouth.
More from Dr. Uralets…
“…We tried your topical prohormone product, Pro-Vigor ® on volunteers. It does not cause dramatic changes in urinary steroid profile, which is good. Results for Andro are difficult to interpret, because amplification in urinary steroid profile is very moderate and fluctuations due to urine density hide the Andro effect. T/E elevation is minimal and far below positive cutoff. I am waiting for your promised samples and, please send another bottle of Pro-Vigor ®. Our “volunteers” were very enthusiastic, they consumed it all…”
Continuous Support of Hormonal Production
Topical delivery provides “steady-state” support of testosterone production. It supports the natural daily release of testosterone and nortestosterone and does not cause “unnatural” spikes as observed with high doses of oral “andro” products. These high steady-state concentrations of testosterone are believed necessary to experience the many benefits of testosterone including increased muscle size, strength, energy and libido.
Orally swallowed prohormones only cause a temporary spike in testosterone levels. In order to keep a steady-state level of the hormone in the body, you must take these products by mouth every 4 hours. This is expensive and wasteful.
Another advantage to “steady state” levels is that the limiting factor in converting these precursors to testosterone is the ability of the body to replenish these enzymes. High one-time dosages that cause spikes overwhelm the capacity of the body’s enzymes and “spillover” takes place. The body then converts the hormones into unwanted metabolites which reduce the effectiveness and increase the likelihood of side effects. Lower multiple dosages or steady state release ensures better utilization and more complete conversion.
In an effort to continue to study the metabolic and physiological effects of transdermal hormones. We analyzed 24 hours of urine samples on a subject using Pro-Performance ®. The purpose of this testing was to confirm that topical application provided for steady state levels of nortestosterone as determined by the presence of it’s urine metabolites. Previous studies of the urine metabolites after oral norandrostenedione use have shown abnormal urine metabolites confirming rapid liver degradation and therefore ineffective conversion to nortestosterone.
Here are the results from Dr. Uralets at Quest Diagnostics
“Your eleven urine samples have been tested. Only three metabolites show up, and they are identical to common Nandrolone metabolites: 19-norandrosterone (1), 19-noretiocholanolone (2) and 19-norepiandrosterone. No specific metabolites of 19-nor-4-androsten-3,17-dione and -diol have been detected. Urine concentrations of (1) vary between 500 and 1800 ng/mL and (2) between 200 and 800 ng/mL, with (1) to (2) ratio being consistent with Nandrolone administration (3:1). These concentrations are pretty steady, during the 24 hour period, comparing to those we observed for oral forms I would certainly expect from parenteral application. Concentrations seem to depend more on urine density, rather than on time passed from the application. This range of concentrations corresponds to that of the high end of Nandrolone dosages.”
“Only three metabolites showed up in the urine and they were identical to common Nandrolone metabolites: 19-norandrosterone, 19-noretiocholanolone and 19-norepiandrosterone. No specific metabolites of 19-nor-4-androsten-3,17-dione and -diol were detected. This confirmed that Pro-Performance ® absorbed and fully converted to nortestosterone.”
“There was three times as much 19-norandrosterone as 19-noretiocholanolone. Urine concentrations of 19-norandrosterone varied between 500 and 1800 ng/mL and 19-noretiocholanolone between 200 and 800 ng/mL. These ratios and quantities were consistent with administration of Nandrolone at the high end of dosing! The concentrations were pretty steady, during 24 hours period, compared to those observed for oral forms.”
“Our studies show that the use of topical phytoandrogens create steady-state levels of testosterone in the blood stream and saliva but do not result in abnormal urine levels of testosterone, or a testosterone/epitestosterone ratio greater than six. Ironically, due to rapid conversion in the liver, oral dosing is not capable of maintaining steady-state levels of testosterone in the blood and may cause short term elevations in the T/E ratio.”
Enhanced Conversion of Androgen Precursors to Testosterone
The optimal combination of androstenedione and androstenediol in a “steady state” delivery allows for more efficient enzymatic conversion to testosterone. It seems that the 3ßHSD enzyme that converts androstenediol to testosterone is not subject to the same rate limiting factors that is the 17ßHSD enzyme (that converts androstenedione to testosterone). The 17ßHSD enzyme requires high ATP levels, therefore it may require large amounts of carbohydrates or supplements that support liver ATP such as pyruvate, phosphates and niacin to function optimally and it is also less active in men than in woman. So why use androstenedione at all? Answer: Because there is a theoretical reason to combine both androstenedione and androstenediol.
This is due to the fact that they use different enzymes for conversion to testosterone. When used together they have an additive effect in enhancing testosterone production, while at the same time minimizing the potential for overloading either enzyme. This allows increased benefits with a reduced potential of unwanted effects or waste. Also, androstenedione directly stimulates the CNS and provides for a greater boost.
Sublingual Delivery ( Pro-Boost ®)
Advantages of Cyclodextrin Orally Dissolved Delivery
Cyclodextrin based prohormones are dissolved in the mouth for rapid short acting (4 to 6 hours) peak in hormones. The result: Far greater effects at lower doses. In fact, clinical tests have shown that Cyclo Andro-4 diol provides up to 300% greater increases in testosterone at _ the dose of swallowed androstenediol capsules.
What are cyclodextrins?
Cyclodextrins are a form of linked carbohydrates. They’re formed by an enzymatic synthesis that begins with starch. The enzymes, called transglycosidases, are derived from bacteria. What these enzymes do is couple the starch molecules together to form a truncated, conical, molecular structure with a hollow cavity inside.
The inside of this cyclodextrin “cone” is just about the perfect shape and volume to accommodate a steroid molecule. It’s also a non-polar molecule, which means that it has some of the same properties as a fat or oil. The steroid molecule doesn’t just sit inside the cone, it actually attaches to the inside of it. Also, it won’t dissolve in water. However, while the inside of the cyclodextrin cone is non-polar, the outside is polar, which means that it will dissolve in water. What’s the significance of all of this? When a steroid molecule and a cyclodextrin molecule hook up, they form a 1:1 complex. So, while the steroids themselves won’t dissolve in water, a cyclodextrin/steroid complex will. The upshot is that steroid complexes become more absorbable through the oral mucosa.
A lot of clinical research has been published on the use of sublingual cyclodextrin complexes (SCCs) in humans. At the forefront of much of this research has been Josef Pitha of the US Department of Health and Human Services. Pitha has several patents on sublingual cyclodextrin complexes. He’s also authored a journal article where he details the results of an SCC of testosterone on men. In a nutshell, Pitha found that an SCC containing 10mg of testosterone per tablet raised testosterone levels astronomically high (900% over baseline at one hour) and at two hours the levels were still elevated 485%. Compare that with another study that used regular testosterone at 20 times the dosage used in Pitha’s study. Regular testosterone – not complexed with cyclodextrin – only raised testosterone around 500% at the peak.
Another study performed by Stuenkel et.al. showed that testosterone SCCs of 2.5 and 5.0mg raised testosterone levels in hypogonadal men 2341% and 4270% (absolute increases of 1765 ng/dL and 2406 ng/dL) respectively! It took an average of 20 to 30 minutes to achieve maximum blood testosterone levels, but even after eight hours post-dose, the testosterone levels were still elevated 126% for the 2.5mg dose and 195% for the 5.0mg dose. Interestingly enough, the peak levels for estradiol only increased 300% and 340% over baseline, respectively. Remarkable, considering that one usually sees estradiol levels increase proportionally with testosterone levels when other forms of administration are used (i.e. injectable esters and TU orals).
This particular study examined the acute responses to 25mg and 50mg doses of a SCC 4-androstenediol in healthy males. These males had an average baseline testosterone concentrations in the high-normal range. The results, expressed as average percent increases over baseline, are as follows:
Testosterone Increases With Cyclo-Diol ™6
Testosterone Increases With Androdiol ™7
When examining the results of this study and comparing them to the results that these same seven subjects had a few months earlier with regular oral 100mg 4-androstenediol capsules, the first thing that strikes the eye is the different times to peak blood values for the SCC versus the straight oral. The time to peak is much sooner for the SCC than it is for the straight oral; 40 minutes versus 90 minutes. Also, the percent increase at peak is much higher for the 25mg SCC (128%) than it is for the straight oral (49%). That translates to a 261% greater testosterone increase with the SCC over straight oral at one quarter the dosage. Also, the drop off in testosterone levels for the 25mg SCC is quite gradual. Testosterone increases at two hours post-dose were still well above the peak levels experienced with the straight oral 100mg dosage.
Interestingly, a 50mg dose was no more effective than a 25mg dose. This is likely due to the limited capacity for absorption through the sublingual tissues. There’s only so much surface area under your tongue.
Another note of interest was that the variability of testosterone responses with subjects taking the androdiol SCC was extremely low. Contrast this to the oral androdiol study where some subjects had increases of testosterone over 100%, while others had increases of barely 25%. In other words, just about everybody who used SCC experienced the same remarkable surges in free testosterone, whereas those that use(d) oral androdiol experienced across-the-board results.
This leads us to believe that the biggest factor in the variable responses to prohormones may not have anything to do with differing levels of conversion enzymes throughout the body, as is generally assumed. Instead, it looks like it may have more to do with differing absorption capabilities from the gut and/or the differing capacity of people’s livers for deactivating orally ingested prohormones upon first pass.
- US patents 4,596,795, 4,727,064, 4,877,774.
- J. of Pharm Sci, 75 (2), 165-167.
- Pitha did not report the testosterone levels at times before one hour. However, since we know from other studies and from our own study that blood levels peak around 30 minutes with these SSCs, the maximum levels in Pitha’s test were probably substantially higher than those he reported at one hour.
- Lancet, 1974, 1473.
- J. Clin. Endocr. Metab., 72 (5), 1054-1059.
- These data were presented at the International Weightlifting Conference in Lahti, Finland, Nov. 1998. Study funded and supported by LPJ Research Inc. and Substrate Solutions Inc. The results do not constitute an endorsement of 4-androstenediol by the author or Eastern Michigan University.
Androstenedione Sublingual Spray: Clinical Results
This article adds to the limited data about androstenedione by describing clinical studies recently performed on four healthy male subjects, using a new, liposomal encapsulated androstenedione sublingual spray (AndroSpray ™). The tests were conducted by Gary Rheinschild, M.D., a Southern California urological surgeon.
Each subject was tested for baseline total (bound), free and weakly bound, and free testosterone. They then sprayed four sprays of the liposomally encapsulated product under their tongues (100mg androstenedione). Tests for testosterone were repeated at 30 minute intervals for 3 hours. The results for free testosterone are shown in charts. Testosterone levels increased in all four subjects, with increases ranging from 22 to 52%. All four subjects expressed increased energy, strength, and well-being after using the spray. Dr. Rheinschild expressed amazement at the rapidity of the rise in testosterone levels in all four subjects.
While these subjective comments could certainly be due to a placebo effect, the similarity of their responses (without coaching) and the confirmatory increase in blood levels of testosterone would mitigate against the response being artifactual.
Interestingly, subject number four was a 54 year-old bodybuilder who had been injecting himself with testosterone. Even though his baseline free testosterone was already “off the chart” at 285 ng/dl, the androstenedione increased his free testosterone another 23% to a phenomenal 351 ng/dl. Subject number two, a 62 year-old physician, without knowing the blood test results (which later confirmed a 52% increase in free testosterone) – but feeling “as energized as a twenty year old”
These four cases lend further credence to the testosterone-boosting effects of androstenedione.
Supplement mimics testosterone’s effects on brain
Researchers speculate that androstenedione may mimic the effects of testosterone. In the study, 19 rats were castrated and given either testosterone, androstenedione, or a placebo (inactive pill) for 5 weeks, according to a report in the July issue of Endocrinology.
The effects of the hormones were determined by examining sections of the rats’ brains for changes. The team were most interested in the areas of the brain that have the greatest density of receptors for the neurotransmitter vasopressin, a system which is activated by androgens or male hormones.
The vasopressin system is related to thirst, sleep-wake cycles and aggression, and is “a thermometer for actions of androgens on the brain” said senior investigator Dr. Geert DeVries in an interview with Reuters Health. The results show androstenedione “is equally strong in its actions in the brain” as testosterone, said DeVries, a professor of neuroscience and behavior at University of Massachusetts, Amherst.
“It’s not just muscles, or even just the brain, but many systems” that are affected by androstenedione, he said. The findings suggest that “androstenedione, which is traditionally referred to as a weak androgen because of its inability to maintain normal genital function, actually has potent androgenic effects in the brain,” the authors conclude.
Androstenedione effects on the vasopressin in nervation of the rat brain. Villalba C, Auger CJ, De Vries GJ. Center for Neuroendocrine Studies, University of Massachusetts, Amherst Endocrinology 1999;140:3383-3386.
The steroid hormone androstenedione profoundly influences the development and expression of sexual and aggressive behavior. The neural basis of these effects are, however, poorly understood. In this study, we evaluated androstenedione’s ability to maintain vasopressin peptide levels in the gonadal steroid-responsive vasopressin cells, of the bed nucleus of the stria terminalis and the centromedial amygdala, and their projections. Adult male rats were castrated and given testosterone, androstenedione or no hormonal treatment for five weeks. Their brains were then processed for vasopressin immunoreactivity. Androstenedione and testosterone treatment were equally effective in preventing the reduction of vasopressin immunoreactivity associated with castration. Androstenedione may therefore be able to mimic the effects of testosterone on testosterone-responsive neural systems.
An adequate activity of the neurotransmitter dopamine is needed in the brain to stimulate the hypothalamus and pituitary to achieve an anabolic effect. Medical science has proven that increased dopamine production has a positive effect on the following brain functions: thinking, cognitive functions (like memory & decision making), sex drive, mood, drive, strength, coordination, movement, mobility and much more. When dopamine becomes depleted due to physical or psychological stress, testosterone response and therapies will not be as effective. Restoration of dopamine levels will enhance therapy whether it is natural or by replacement.
Medical science has also proven dopamine has a positive impact on growth hormone secretion. Growth hormone secretion is regarded as the key factor for the regeneration of cells and tissue. Increased dopamine production enhances the body’s ability to repair or replace damage and wounded cells.
Dopamine has been proven to reduce prolactin secretion, which is believed to be the cause of appetite. The higher the dopamine levels in the blood, the lower the appetite. It is believed that higher or normalized dopamine blood levels reduces “binge” eating.
Study of the effects of neurotransmitters on the hypothalamus-pituitary-testis function in vitro cell suspension system. Vermes I, Varszegi M, Toth EK, Telegdy G Arch Androl 1979;3(2):127-33.
The effects of different neurotransmitters were tested in vitro on a hypothalamic tissue, collagenase-digested isolated anterior pituitary and Leydig cell suspension system by measuring the testosterone production of the Leydig cells. Neurotransmitters were used in concentrations of 0.25, 1.0, 2.5, 5.0, and 10.0 micrograms/ml incubation medium. Dopamine in doses of 1.0, 2.5, and 5.0 micrograms/ml increased the hypothalamic tissue-induced pituitary-testis activation, while it had no direct effect on pituitary and Leydig cells. Noradrenaline in the concentration range 2.5–10.0 micrograms/ml decreased the luteinizing-hormone-releasing-hormone (LHRH) sensitivity of the pituitary cells. 5.0 and 10.0 micrograms/ml 5-hydroxytryptamine decreased the testosterone production and the hCG sensitivity of the isolated Leydig cells. Carbamylcholine and pilocarpine had no action on the in vitro system at the different levels studied.
Effects of drugs on brain neurotransmitter and pituitary-testicular function in male rats. Vermes I, Toth EK, Telegdy G Horm Res 1979;10(4):222-32.
The effects of different drugs influencing brain neurotransmitter contents have been tested on the pituitary-testicular function in male rats. L-dopa (200 mg/kg body weight, i.p.) increased the dopamine and noradrenaline contents of the hypothalamus, amygdala, striatum and mesencephalon, but it was ineffective as regards the 5-hydroxytryptamine contents of the same brain areas and increased the plasma testosterone level. Alpha-Methyl-p-tyrosine (250mg/kg b.w., i.p.) decreased the dopamine and noradrenaline contents of these brain areas, but it was ineffective to 5-hydroxytryptamine, and decreased the plasma testosterone level. Diethyldithiocarbamate (400 mg/kg b.w., i.p. twice a day) increased the dopamine levels in the hypothalamus, amygdala, striatum and mesencephalon, decreased the noradrenaline contents in the same brain regions but had no effect on the 5-hydroxytryptamine contents of these brain areas or on the testosterone level in the peripheral blood. p-Chlorophenylalanine (300mg/kg b.w., i.p.) decreased the 5-hydroxytryptamine contents of the different brain areas, while it had no effect on the dopamine and noradrenaline levels or on the plasma testosterone level. 5-Hydroxytryptophan (200mg/kg b.w., i.p.) increased the 5-hydroxytryptamine contents of all brain areas studied, but was without effect on the dopamine and noradrenaline contents or the plasma testosterone level. The data suggest that both dopamine and noradrenaline may be involved i