The reliable measurement of serum free testosterone requires equilibrium dialysis. This is not appropriate for clinical use as it is very time consuming and therefore expensive. The amount of bioavailable testosterone can be measured as a percentage of the total testosterone after precipitation of the SHBG bound fraction using ammonium sulphate. The bioavailable testosterone is then calculated from the total testosterone level. This method has an excellent correlation with free testosterone (Tremblay and Dube 1974) but is not widely available for clinical use. In most clinical situations the available tests are total testosterone and SHBG which are both easily and reliably measured. Total testosterone is appropriate for the diagnosis of overt male hypogonadism where testosterone levels are very low and also in excluding hypogonadism in patients with normal/high-normal testosterone levels. With increasing age, a greater number of men have total testosterone levels just below the normal range or in the low-normal range. In these patients total testosterone can be an unreliable indicator of hypogonadal status. There are a number of formulae that calculate an estimated bioavailable or free testosterone level using the SHBG and total testosterone levels. Some of these have been shown to correlate well with laboratory measures and there is evidence that they more reliably indicate hypogonadism than total testosterone in cases of borderline biochemical hypogonadism (Vermeulen et al 1971; Morris et al 2004). It is important that such tests are validated for use in patient populations relevant to the patient under consideration.
^ Jump up to: a b Lazaridis I, Charalampopoulos I, Alexaki VI, Avlonitis N, Pediaditakis I, Efstathopoulos P, Calogeropoulou T, Castanas E, Gravanis A (2011). "Neurosteroid dehydroepiandrosterone interacts with nerve growth factor (NGF) receptors, preventing neuronal apoptosis". PLoS Biol. 9 (4): e1001051. doi:10.1371/journal.pbio.1001051. PMC 3082517. PMID 21541365.
Aromatase inhibitors can boost testosterone on their own, but they can also complement other testosterone boosters. If you take a supplement that increases testosterone without inhibiting the aromatase enzyme (through hypothalamic stimulation, for instance), you may find yourself with more estradiol than you need, a situation that taking an aromatase inhibitor may remedy.
In accordance with sperm competition theory, testosterone levels are shown to increase as a response to previously neutral stimuli when conditioned to become sexual in male rats. This reaction engages penile reflexes (such as erection and ejaculation) that aid in sperm competition when more than one male is present in mating encounters, allowing for more production of successful sperm and a higher chance of reproduction.
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A: Depo-Testosterone is a brand name medication that contains testosterone cypionate. Depo-Testosterone is given as an intramuscular injection. The medication is indicated for replacement therapy for men that have conditions associated with symptoms of deficiency in the hormone or absence of testosterone produced in the body. Conditions that can be associated with low testosterone include: delayed puberty, impotence and hormonal imbalances. Testosterone is a sex hormone that is naturally produced in the male testicles. In women, small amounts of testosterone is produced in the ovaries and by the adrenal system. Testosterone is available in various medications for testosterone replacement therapy. Different forms of testosterone (e.g. cypionate, enanthate etc) are contained in different brand name medications. Jen Marsico, RPh
Epidemiological studies have also assessed links between serum testosterone and non-coronary atherosclerosis. A study of over 1000 people aged 55 years and over found an inverse correlation between serum total and bioavailable testosterone and the amount of aortic atherosclerosis in men, as assessed by radiological methods (Hak et al 2002). Increased intima-media thickness (IMT) is an early sign of atherosclerosis and has also been shown to predict cardiovascular mortality (Murakami et al 2005). Cross-sectional studies have found that testosterone levels are negatively correlated with carotid IMT in independently living men aged 74–93 years (van den Beld et al 2003), diabetic men (Fukui et al 2003) and young obese men (De Pergola et al 2003). A 4-year follow up study of the latter population showed that free testosterone was also inversely correlated with the rate of increase of IMT (Muller et al 2004).
No one will argue with the well-established fact that the dramatic lows of testosterone as seen in castration or other significant primary testicular disturbances such as those induced by chemotherapy, radiation therapy, congenital problems, or as seen in secondary testicular insufficiency (eg, large compressive pituitary or hypothalamic tumors) produce dramatic signs and symptoms of testosterone deficiency that require testosterone replacement therapy. Less clear, or at least more controversial, is the necessity of treating the gentler reduction of testosterone seen in the aging process.
Testosterone is considered to be the "male hormone" that's produced in men by the testes. Although women's ovaries produce some testosterone, the hormone is produced in much higher concentrations in men and it is responsible for many of the secondary sex characteristics seen in men such as a deeper voice and hair on the chest, in addition to contributing to a healthy libido, building muscle mass, and maintaining energy levels.
Directions — SUGGESTED USE: As a dietary supplement take 3 capsules daily, preferably with a meal, or as directed by a healthcare professional. — Take two capsules with a meal twice a day. On days that you are not training, take two capsules in the morning and two capsules at night. On days that you train, take two capsules about an hour before workouts and take two capsules in the morning or at night depending on when you train.
The effects of testosterone in humans and other vertebrates occur by way of multiple mechanisms: by activation of the androgen receptor (directly or as DHT), and by conversion to estradiol and activation of certain estrogen receptors. Androgens such as testosterone have also been found to bind to and activate membrane androgen receptors.
When testosterone and endorphins in ejaculated semen meet the cervical wall after sexual intercourse, females receive a spike in testosterone, endorphin, and oxytocin levels, and males after orgasm during copulation experience an increase in endorphins and a marked increase in oxytocin levels. This adds to the hospitable physiological environment in the female internal reproductive tract for conceiving, and later for nurturing the conceptus in the pre-embryonic stages, and stimulates feelings of love, desire, and paternal care in the male (this is the only time male oxytocin levels rival a female's).
A: According to the package insert, there are several longer-term side effects that have occurred with testosterone therapy. Testosterone can stimulate the growth of cancerous tissue. Prostate cancer or enlargement of the prostate can develop during prolonged therapy with testosterone, and these conditions are more likely to occur in elderly men. In patients receiving testosterone therapy, tests for prostate cancer should be performed as is current practice. Androgen therapy, such as testosterone, can cause a loss of blood sugar control in patients with diabetes. Close monitoring of blood glucose is recommended. Male patients can experience feminization during prolonged therapy with testosterone. The side effects of feminization include breast soreness and enlargement. These side effects are generally reversible when treatment is stopped. Hair loss resembling male pattern baldness has also occurred. Sexual side effects including decreased ejaculatory volume and low sperm counts have occurred in patients receiving long-term therapy or excessive doses. For more information, please consult with your health care provider and visit //www.everydayhealth.com/drugs/testosterone. Michelle McDermott, PharmD
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Hypogonadism is a disease in which the body is unable to produce normal amounts of testosterone due to a problem with the testicles or with the pituitary gland that controls the testicles. Testosterone replacement therapy can improve the signs and symptoms of low testosterone in these men. Doctors may prescribe testosterone as injections, pellets, patches or gels.