Pharmacokinetics and pharmacodynamics of subcutaneous testosterone implants in hypogonadal men

Challenges in the care of transgender and gender-diverse youth: an endocrinologist's view

An increasing number of transgender and gender-diverse (TGD) youth (early pubertal through to late adolescent, typically 9-10 through to 18 years of age) are seeking medical services to bring their physical sex characteristics into alignment with their gender identity - their inner sense of self as male or female or somewhere on the gender spectrum. Compelling research has demonstrated the clear mental health - even life-saving - benefits of gender-affirming care, but current clinical practice guidelines and standards of care are based on only several short-term and a few medium-term outcomes studies complemented by expert opinion. Nevertheless, although the relative paucity of outcomes data raises concerns, the stance of not intervening until more is known is not a neutral option, and large observational studies evaluating current models of care are necessary and are now underway. This Review highlights key advances in our understanding of transgender and gender-diverse youth, the challenges of providing gender-affirming care, gaps in knowledge and priorities for research.

Short-acting testosterone appears to have lesser effect on male reproductive potential compared to long-acting testosterone in mice

Objective

To compare the effect of exogenous short-acting and long-acting testosterone on male reproductive potential in mice.

Design

In vivo mouse model.

Setting

University-based basic science research laboratory.

Animals

A total of 30 wild-type C57BL/6 male and female mice were used for this experimentation. The male mice were used for control group and testosterone supplementation, while both male and female mice were used for the breeding portion of the study.

Interventions

Exogenous testosterone was administered either in short-acting formulation (Monday-Wednesday-Friday dosing schedule, testosterone propionate 0.2 mg/kg), or long-acting formulation (3-month dosing schedule - testosterone pellets 150 mg) to male mice.

Main Outcome Measures

Time to pregnancy, Luteinizing hormone (LH) levels, and testicular weight.

Results

Mice treated with long-acting testosterone appear to have longer time to pregnancy when compared to wild-type (33 ± 11 vs 23 ± 2.6 days, p ≤ 0.05) and mice that received short-acting testosterone propionate (26 ± 5.9 days). Mice treated with long-acting testosterone had smaller testes weight when compared to control (0.08 ± 0.01 vs 0.11 ± 0.01g; p ≤ 0.01), while the short-acting testosterone treated mice had similar testis weight when compared to control (0.09 ± 0.02 vs 0.11 ± 0.01g; ns). The serum testosterone level was elevated in mice that received testosterone pellets (285.78 ng/dL) and testosterone propionate (122.16 ng/dL) versus control (68.4 ng/dL). In mice that received long-acting testosterone pellets, LH levels at 3 months were almost undetectable while those that received short-acting testosterone remained similar to control (0.017 ± 0.058 vs 0.348 ± 0.232 IU/L; p ≤ 0.01). Female reproductive potential parameters including litter size and pup weight were collected and observed to have no difference between groups.

Conclusion

Through a mouse breeding study, mice that received short-acting testosterone were shown to have fertility potential similar to wild-type male mice. Long-acting exogenous testosterone appeared to impair male reproductive capacity and LH levels when compared to short-acting testosterone. Short-acting testosterone appeared to cause less LH suppression. Identifying strategies to increase testosterone while simultaneously preserving male fertility is important for treating young men with hypogonadism.

Dihydrotestosterone: Biochemistry, Physiology, and Clinical Implications of Elevated Blood Levels

Benefits associated with lowered serum DHT levels after 5α-reductase inhibitor (5AR-I) therapy in men have contributed to a misconception that circulating DHT levels are an important stimulus for androgenic action in target tissues (e.g., prostate). Yet evidence from clinical studies indicates that intracellular concentrations of androgens (particularly in androgen-sensitive tissues) are essentially independent of circulating levels. To assess the clinical significance of modest elevations in serum DHT and the DHT/testosterone (T) ratio observed in response to common T replacement therapy, a comprehensive review of the published literature was performed to identify relevant data. Although the primary focus of this review is about DHT in men, we also provide a brief overview of DHT in women. The available published data are limited by the lack of large, well-controlled studies of long duration that are sufficiently powered to expose subtle safety signals. Nonetheless, the preponderance of available clinical data indicates that modest elevations in circulating levels of DHT in response to androgen therapy should not be of concern in clinical practice. Elevated DHT has not been associated with increased risk of prostate disease (e.g., cancer or benign hyperplasia) nor does it appear to have any systemic effects on cardiovascular disease safety parameters (including increased risk of polycythemia) beyond those commonly observed with available T preparations. Well-controlled, long-term studies of transdermal DHT preparations have failed to identify safety signals unique to markedly elevated circulating DHT concentrations or signals materially different from T.

Adult-onset hypogonadism: evaluation and role of testosterone replacement therapy

Testosterone deficiency (TD) has become a growing concern in the field of men’s sexual health, with an increasing number of men presenting for evaluation of this condition. Given the increasing demand for testosterone replacement therapy (TRT), a panel of experts met in August of 2015 to discuss the treatment of men who present for evaluation in the setting of low or normal gonadotropin levels and the associated signs and symptoms of hypogonadism. This constellation of factors can be associated with elements of both primary and secondary hypogonadism. Because this syndrome commonly occurs in men who are middle-aged and older, it was termed adult-onset hypogonadism (AOH). AOH can be defined by the following elements: low levels of testosterone, associated signs and symptoms of hypogonadism, and low or normal gonadotropin levels. Although there are significant benefits of TRT for patients with AOH, candidates also need to understand the potential risks. Patients undergoing TRT will need to be monitored regularly because there are potential complications that can develop with long-term use. This review is aimed at providing a deeper understanding of AOH, discussing the benefits and risks of TRT, and outlining each modality of TRT in use for AOH.

Diagnosis and management of testosterone deficiency

Testosterone supplementation therapy (TST) use has dramatically increased over the past decade, due to the availability of newer agents, aggressive marketing, and an increasing incidence of testosterone deficiency (TD). Despite the increase in TST, a degree of ambiguity remains as to the exact diagnostic criteria of TD, and administration and monitoring of TST. One explanation for this phenomenon is the complex role testosterone plays in multiple physiologic pathways. Numerous medical co-morbidities and medications can alter testosterone levels resulting in a wide range of nonspecific clinical signs and symptoms of TD. The diagnosis is also challenging due to the lack of a definitive serum total testosterone level that reliably correlates with symptoms. This observation is particularly true in the aging male and is exacerbated by inconsistencies between different laboratory assays. Several prominent medical societies have developed guideline statements to clarify the diagnosis, but they differ from each other and with expert opinion in several ways. Aside from diagnostic dilemmas, there are numerous subtle advantages and disadvantages of the various testosterone agents to appreciate. The available TST agents have changed significantly over the past decade similar to the trends in the diagnosis of TD. Therefore, as the usage of TST increases, clinicians will be challenged to maintain an up-to-date understanding of TD and TST. The purpose of this review is to provide a clear description of the current strategies for diagnosis and management of TD.

A Review of Testosterone Pellets in the Treatment of Hypogonadism

Currently, the most popular form of testosterone replacement is the topical gels that require daily applications and incur a risk of transfer of testosterone to partners and family. One of the problems with testosterone replacement is the short half-life of testosterone. A long-acting formulation is appealing to patients and physicians. In 1972, fused crystalline testosterone pellets were approved in the USA by the FDA but they were not marketed until 2008. Pharmacokinetics studies were available on a different formulation from which much can be learned and applied to the current formulation, Testopel®. The decay kinetics, pituitary suppression, and effect on other sex steroids are reviewed as well as the short-term complication rates. This review should provide the testosterone pellet implanter a better understanding of the physiology of testosterone pellet supplementation for hypogonadism.

The effects of bed-rest and countermeasure exercise on the endocrine system in male adults: evidence for immobilization-induced reduction in sex hormone-binding globulin levels

BACKGROUND AND AIM

There is limited data on the effects of inactivity (prolonged bed-rest) on parameters of endocrine and metabolic function; we therefore aimed to examine changes in these systems during and after prolonged (56- day) bed-rest in male adults.

SUBJECTS AND METHODS

Twenty healthy male subjects underwent 8 weeks of strict bed-rest and 12 months of follow-up as part of the Berlin Bed Rest Study. Subjects were randomized to an inactive group or a group that performed resistive vibration exercise (RVE) during bed-rest. All outcome parameters were measured before, during and after bed-rest. These included body composition (by whole body dual X-ray absorptiometry), SHBG, testosterone (T), estradiol (E2), PRL, cortisol (C), TSH and free T3 (FT3).

RESULTS

Serum SHBG levels decreased in inactive subjects but remained unchanged in the RVE group (p<0.001). Serum T concentrations increased during the first 3 weeks of bed-rest in both groups (p<0.0001), while E2 levels sharply rose with re-mobilization (p<0.0001). Serum PRL decreased in the control group but increased in the RVE group (p=0.021). C levels did not change over time (p≥0.10). TSH increased whilst FT3 decreased during bed-rest (p all ≤0.0013).

CONCLUSIONS

Prolonged bed-rest has significant effects on parameters of endocrine and metabolic function, some of which are related to, or counteracted by physical activity.

Treating hypogonadism in younger males

IMPORTANCE OF THE FIELD

Hypogonadism in the young and middle-aged male is a well-established clinical entity. The majority of the patients have primary gonadal insufficiency with Klinefelter syndrome a common cause. Secondary hypogonadism in these age groups can be congenital, secondary to medications, or associated with a hypothalamic-pituitary mass or inflammatory lesions. Signs and symptoms in males with hypogonadism can include impaired sexuality, decreased muscle strength, increased body fat, decreased bone mass, impaired mood and mild anemia; in young patients puberty can be delayed. Several new treatment modalities have become available in recent years and a number of future compounds are in development.

AREAS COVERED IN THIS REVIEW/WHAT THE READER WILL GAIN

This review explores the treatment options for children, young adult and middle-aged males with hypogonadism related to various etiologies, including currently available and future testosterone formulations and other non-testosterone compounds. The long-term treatment effects, particularly on prostate health, remain unclear and may be particularly relevant for the younger patient initiated on chronic therapy; treatment monitoring and recommended clinical follow-up based on current guidelines are also reviewed.

TAKE HOME MESSAGE

Hypogonadism in younger males can be the result of a diversity of etiologies. Treatment options for hypogonadism and induction of puberty have expanded and can be individualized based on patient preference, side effect profile, and a number of other parameters.

Male contraception: A realistic option?

This review illustrates the principle of hormonal male contraception and gives an overview of current trials aiming at the development of a marketable hormonal contraceptive for men. The principle of male hormonal contraception is based on strong suppression of gonadotropins in order to arrest spermatogenesis at the spermatogonial stem cell level, thus leading to azoospermia or severe oligozoospermia. Until now, it has not been possible to interrupt spermatogenesis effectively without simultaneously inhibiting the production of androgens by Leydig cells, resulting in a deficiency of extra-testicular androgens. Therefore, testosterone needs to be replaced. By administering exogenous testosterone alone azoospermia can be reached in East Asians, whereas azoospermia is only achieved in two-thirds of Caucasian volunteers so that in these men an additional agent is required. Currently injectable testosterone combined with gestagens or administered as implants are being tested for possible licensing. Although scrotal and non-scrotal testosterone patches, orally administered testosterone undecanoate and testosterone gels are generally well tolerated and provide stable testosterone levels in the normal range, their use showed generally disappointing efficacy due to insufficient gonadotropin suppression. Further large multi-centre studies are required to establish the contraceptive efficacy of the most promising steroid combinations.

The benefits and risks of testosterone replacement therapy: a review

Increased longevity and population aging will increase the number of men with late onset hypogonadism. It is a common condition, but often underdiagnosed and undertreated. The indication of testosterone-replacement therapy (TRT) treatment requires the presence of low testosterone level, and symptoms and signs of hypogonadism. Although controversy remains regarding indications for testosterone supplementation in aging men due to lack of large-scale, long-term studies assessing the benefits and risks of testosterone-replacement therapy in men, reports indicate that TRT may produce a wide range of benefits for men with hypogonadism that include improvement in libido and sexual function, bone density, muscle mass, body composition, mood, erythropoiesis, cognition, quality of life and cardiovascular disease. Perhaps the most controversial area is the issue of risk, especially possible stimulation of prostate cancer by testosterone, even though no evidence to support this risk exists. Other possible risks include worsening symptoms of benign prostatic hypertrophy, liver toxicity, hyperviscosity, erythrocytosis, worsening untreated sleep apnea or severe heart failure. Despite this controversy, testosterone supplementation in the United States has increased substantially over the past several years. The physician should discuss with the patient the potential benefits and risks of TRT. The purpose of this review is to discuss what is known and not known regarding the benefits and risks of TRT.

Anabolic and androgenic activity of 19-norandrostenedione after oral and subcutaneous administration--analysis of side effects and metabolism

One of the most frequently misused steroid precursors (prohormones) is 19-norandrostenedione (estr-4-ene-3,17-dione, NOR). Recently we have show that NOR stimulates skeletal muscle growth after s.c. administration in a highly selective manner but exhibits only weak androgenic activity in rats. Because most abusers take NOR orally, the aim of this study was to compare the anabolic and androgenic potency of NOR between s.c. and oral application. Orchiectomised rats were treated with NOR either s.c. (1 mg/kg BW/day) or orally (0.1, 1 and 10 mg/kg BW/day). The tissue weights of the levator ani, the seminal vesicle and the prostate were analysed to determine the anabolic and androgenic activity. Heart and liver wet weights were examined to identify side effects. Serum concentrations of NOR and its metabolite nandrolone (NT) were determined. GCMC analysis revealed that free and glucuronidated NOR and NT were detectable in the serum after oral and s.c. administration and that NOR was converted to NT in comparable amounts independent of the route of administration. In agreement to our previous study s.c. application of NOR stimulates skeletal muscle growth but has only weak androgenic effects. In contrast, after oral administration of NOR neither stimulation of the prostate nor the levator ani could be observed in the doses administered in this study. Interestingly, and in contrast to s.c. treatment, oral administration of NOR resulted in a dose-dependent decrease of body weight. In summary, oral administration of NOR, at least in the rat, seems to be a very ineffective strategy for stimulating skeletal muscle mass increases but may be associated with side effects.

Testosterone treatment in elderly men

Testosterone has been used in testicular and hypothalamo-pituitary diseases since the 1940s. There is growing interest in the use of testosterone in aging men, and this has stimulated research into the benefits of male hormone replacement. Testosterone treatment of men with hypogonadism might have beneficial effects on body composition, muscle strength, sexual function, and cognition. There are several modes of administration of the male hormone, with injectable testosterone esters and implanted testosterone pellets being the mainstay of treatment until recently. These preparations are increasingly being replaced by transdermal patches, gels, and long-acting parenteral preparations. Testosterone patches and gels are ideally for elderly men. Treatment with the male hormone is relatively safe, if patients are selected appropriately and monitored carefully. The most important adverse effects are on the prostate. In this review, we briefly discuss the indications, contraindications, and benefits of testosterone treatment. Further, we list the adverse effects, advantages, and disadvantages of various testosterone preparations in elderly men.

Current and future testosterone delivery systems for treatment of the hypogonadal male

BACKGROUND

Hypogonadism is manifest in all age groups, and a growing elderly population is requiring treatment for testosterone deficiency, presenting new safety challenges, as many of these individuals present with comorbidities and significant risk profiles.

OBJECTIVE

To discuss testosterone replacement modalities, their advantages and disadvantages, and provide a discussion of safety issues.

METHODS

We reviewed the literature regarding testosterone replacement therapy and have provided a summary of our most outstanding findings.

CONCLUSION

Potential benefits of testosterone replacement therapy include increased lean body mass, heightened libido, increased bone density and elevation of mood. Some disadvantages are clearly defined, while others require further investigation. Patient and physician must cooperate to agree on an individual patient's most appropriate and tolerable route of administration.

Testosterone therapy in the aging male

The decline, with aging, in serum concentrations of biologically active forms of testosterone in men is an indisputable fact and some men will eventually develop symptoms of late-onset hypogonadism (LOH) with its clinical consequences. LOH reduces quality of life and may pose important risk factors for frailty, changes in body composition, cardiovascular disease, sexual dysfunction and osteoporosis. Testosterone supplementation in cases of LOH will restore serum testosterone levels into the physiologic range; will restore metabolic parameters to the eugonadal state, increase muscle mass, strength, and function; maintaine or improve BMD reducing fracture risk; will improve neuropsychological function (cognition and mood); libido and sexual functioning; and enhance quality of life. The ultimate goals, however, are to maintain or regain a high quality of life, to reduce disability, to compress major illnesses into a narrow age range and to add life to years. To achieve these goals men must also adjust their lifestyle to optimize dietary habits, as well as to exercise and to abstain from smoking life-long. Monitoring these patients is a shared responsibility that cannot be taken lightly. The physician must emphasize to the patient the need for periodic evaluations and the patient must agree to comply with these requirements. The physician's evaluation should include an assessment of the clinical response and monitoring must be tailored to the indications and individual needs of the patient.

Drug insight: testosterone preparations

Testosterone has been used for substitution therapy in testicular and hypothalamopituitary diseases for almost six decades, with injectable testosterone esters and implanted testosterone pellets being the mainstay of treatment. Growing interest in the possible use of testosterone in nonclassical situations such as male contraception, aging (late-onset hypogonadism), muscle-wasting conditions like HIV, erectile dysfunction, and female hypoactive sexual disorder has stimulated research, leading to the development of several new modes of administration of testosterone. Transdermal patches, gels, mucoadhesive sustained-release buccal tablets and long-acting testosterone esters are designed to provide testosterone levels that approximate normal physiologic levels, to improve patient acceptability, and to further increase the number of treatment options available. In this Review, we briefly describe the chemistry, mechanism of action, and metabolism of testosterone. We then discuss the pharmacokinetics, advantages, and disadvantages of various formulations and summarize the various preparations currently available.

Testosterone treatment comes of age: new options for hypogonadal men

Male hypogonadism is one of the most frequent, but also most underdiagnosed, endocrinopathies. However, the required testosterone treatment is simple and very effective if properly administered. Although testosterone has been available for clinical use for seven decades, until quite recently the treatment modalities were far from ideal. Subdermal testosterone pellets require minor surgery for insertion and often cause local problems. The injectable testosterone enanthate, for a long period the most frequently used mode of administration, lasts for two to four weeks, but produces supraphysiological levels initially and low levels before the next injection. The oral testosterone undecanoate has to be taken three times daily, has an uncertain absorption pattern and results in peaks and valleys of serum testosterone levels throughout the day. With the advent of transdermal testosterone preparations, the desired physiological serum levels could be achieved for the first time. Scrotal testosterone patches were the first to fulfil this requirement. These were followed by nonscrotal skin patches, which, however, cause considerable skin reactions including erythema and blisters. Recently introduced, invisible transdermal testosterone gels increased the intervals of application and are now slowly replacing other modalities. A mucoadhesive buccal testosterone tablet with sustained release is also a recent competing modality. Finally, injectable testosterone undecanoate in castor oil was made into a real depot preparation requiring only four injections per year for replacement therapy. These new preparations with a desired pharmacokinetic testosterone profile give the patient a real choice and make treatment easier. Based on pharmacogenetic considerations taking the androgen receptor polymorphism into account, treatment may be individualized for each patient in the future.

Testosterone Hormone Replacement Therapy: State-of-the-Art and Emerging Technologies

In the human male, testosterone is the major circulating androgen. The clinical effects of androgen are numerous, and testosterone deficiency is associated with a number of clinical abnormalities. At present, a variety of preparations containing testosterone is available for the treatment of androgen deficiency. Ideally, those treatments have to produce and maintain physiologic serum concentrations of the hormone. This article reviews the current existing testosterone dosage forms on the market with their advantages and drawbacks and examines new and emerging technology developments concerning this therapy. In particular, the latest innovations in transdermal delivery are explored.

Male hypogonadism : an update on diagnosis and treatment

Male hypogonadism is one of the most common endocrinologic syndromes. The diagnosis is based on clinical signs and symptoms plus laboratory confirmation via the measurement of low morning testosterone levels on two different occasions. Serum luteinizing hormone and follicle-stimulating hormone levels distinguish between primary (hypergonadotropic) and secondary (hypogonadotropic) hypogonadism. Hypogonadism associated with aging (andropause) may present a mixed picture, with low testosterone levels and low to low-normal gonadotropin levels. Androgen replacement therapy in hypogonadal men has many potential benefits: improved sexual function, an enhanced sense of well-being, increased lean body mass, decreased body fat, and increased bone density. However, it also carries potential risks, including the possibility of stimulating the growth of an occult prostate cancer. The benefits of androgen therapy outweigh the risks in men with classic hypogonadism. However, for men with mild hypogonadism or andropause, the balance between benefits and risks is not always clear. Unfortunately, studies to date have included too small a number of patients and have been too short in duration to provide meaningful data on the long-term risks versus the benefits of androgen replacement therapy in these populations. Several products are currently marketed for the treatment of male hypogonadism. Weekly-to-biweekly injections of testosterone cypionate (cipionate) or testosterone enanthate (enantate) are widely used, as they are economical and generally well tolerated. However, once-daily transdermal therapies have become increasingly popular and now include both patch and gel systems. Intramuscular injection of testosterone undecanoate is an attractive new therapy that can be administered quarterly. To confirm an adequate replacement dosage, assessment of clinical responses and measurement of serum testosterone levels generally suffice. For selected men, serial measurement of bone mineral density during androgen therapy might be helpful to confirm end-organ effects. For men aged >50 years, we advocate measurement of hematocrit for detection of polycythemia and a digital rectal examination with a serum prostate-specific antigen level measurement for prostate cancer screening during the first few months of androgen therapy. Subsequently, a hematocrit should be obtained yearly or after changes in therapy, and annual prostate cancer screening can be offered to the patient after a discussion of its risks and benefits.

Testosterone replacement therapy for male hypogonadism: Part III. Pharmacologic and clinical profiles, monitoring, safety issues, and potential future agents

Male hypogonadism is associated with potentially distressing adverse effects on diverse organs and tissues. These include sexual dysfunction, particularly diminished libido, as well as mood disturbances, reduced lean body mass, and increased adipose-tissue mass. A wide range of effective and well-tolerated options exists. These include relatively noninvasive therapies, such as testosterone (T) gels and T patches; slightly more invasive treatments, such as the T buccal system; and invasive therapies, such as intramuscular T injections and subcutaneous depot implants (T pellets). Testosterone replacement therapy (TRT) can be individualized to enhance patient health and well-being. Screening and ongoing monitoring are necessary to ensure both the efficacy and safety of TRT, particularly prostate safety. Investigational agents, including selective androgen receptor modulators, may offer new pharmacodynamic and/or pharmacokinetic properties that enhance outcomes of TRT.

Androgen Replacement Therapy

The major goal of androgen substitution is to replace testosterone at levels as close to physiological levels as is possible. For some androgen-dependent functions testosterone is a pro-hormone, peripherally converted to 5alpha-dihydrotestosterone (DHT) and 17beta-estradiol (E2), of which the levels preferably should be within normal physiological ranges. Furthermore, androgens should have a good safety profile without adverse effects on the prostate, serum lipids, liver or respiratory function, and they must be convenient to use and patient-friendly, with a relative independence from medical services. Natural testosterone is viewed as the best androgen for substitution in hypogonadal men. The reason behind the selection is that testosterone can be converted to DHT and E2, thus developing the full spectrum of testosterone activities in long-term substitution. The mainstays of testosterone substitution are parenteral testosterone esters (testosterone enantate and testosterone cipionate) administered every 2-3 weeks. A major disadvantage is the strongly fluctuating levels of plasma testosterone, which are not in the physiological range at least 50% of the time. Also, the generated plasma E2 is usually supraphysiological. A major improvement is parenteral testosterone undecanoate producing normal plasma levels of testosterone for 12 weeks, with normal plasma levels of DHT and E2 also. Subcutaneous testosterone implants provide the patient, depending on the dose of implants, with normal plasma testosterone for 3-6 months. However, their use is not widespread. Oral testosterone undecanoate dissolved in castor oil bypasses the liver via its lymphatic absorption. At a dosage of 80 mg twice daily, plasma testosterone levels are largely in the normal range, but plasma DHT tends to be elevated. For two decades transdermal testosterone preparations have been available and have an attractive pharmacokinetic profile. Scrotal testosterone patches generate supraphysiological plasma DHT levels, which is not the case with the nonscrotal testosterone patches. Transdermal testosterone gel produces fewer skin irritations than the patches and offers greater flexibility in dosage. Oromucosal testosterone preparations have recently become available. Testosterone replacement is usually of long duration and so patient compliance is of utmost importance. Therefore, the patient must be involved in the selection of type of testosterone preparation. Administration of testosterone to young individuals has almost no adverse effects. With increasing age the risk of adverse effects on the prostate, the cardiovascular system and erythropoiesis increases. Consequently, short-acting testosterone preparations are better suited for aging androgen-deficient men.

Estimating the contribution of the prostate to blood dihydrotestosterone

The prostate strongly expresses type 2 5 alpha-reductase, which avidly converts on entry most testosterone (T) to 5 alpha-dihydrotestosterone (DHT). However, the quantitative contribution of the prostate to blood DHT is uncertain. We evaluated prostatic contribution to blood DHT by comparing the blood DHT concentrations in androgen-deficient patients with or without a prostate while they were receiving standard dose of T replacement. Androgen-deficient males (ADM) and female to male (F2M) transsexuals were studied in 2 centers, with both groups receiving either testosterone ester injections (250 mg mixed T esters) every 1 wk (Amsterdam) or 800 mg subdermal T implantation (Sydney). Among 39 Dutch patients, F2M (n = 21) were younger and smaller in physique than ADM (n = 18). One week (+/-1 d) after an injection, plasma DHT concentrations were 1.6 +/- 0.2 (F2M) vs. 1.4 +/- 0.2 (ADM) nmol/liter (P = 0.47), but the postinjection time interval to blood sampling was shorter in F2M (5.9 +/- 0.4 vs. 7.2 +/- 0.3 d; P = 0.01). Covariance adjustment for time since last injection, age, and physique did not change the lack of significant difference in postinjection plasma DHT concentration. The rapid and wide excursions in plasma T concentrations after an im T ester injection make the timing of blood sampling critical. To remove confounding by this variable, the experiment was repeated at a second site in similar patients, but using a depot T that achieves steady-state delivery for prolonged periods. Among 29 Australian patients, before and 1 month after subdermal implantation of 800 mg T, plasma DHT concentrations were not significantly different between groups [F2M, 1.1 +/- 0.1 (n = 14); ADM, 1.3 +/- 0.1 (n = 15); P = 0.28]. Correction for covariates, including age, height, weight, body surface area, and body mass index, did not influence the lack of significant difference between treated groups. As both modes of T administration yielded similar plasma DHT concentrations regardless of the presence of a prostate, this study indicates that the normal human prostate is not a major contributor to circulating blood DHT concentrations.

Treatment options for a patient experiencing pruritic rash associated with transdermal testosterone: a review of the literature

A 22-year-old man with hypogonadotropic hypogonadism was receiving monthly intramuscular injections of testosterone replacement therapy. The patient refused to self-administer the injections because of discomfort, so the therapy was switched to testosterone patches. He experienced a pruritic, macular, erythematous rash underneath the reservoir area of two different transdermal formulations, which did not improve after pretreatment with topical corticosteroids. Eventually, he tolerated application of a testosterone gel and his serum testosterone levels returned to normal after 1 month of therapy. Commercially available and investigational testosterone products and therapeutic monitoring guidelines for androgen replacement are reviewed.

Dose-finding study of oral desogestrel with testosterone pellets for suppression of the pituitary-testicular axis in normal men

Prototype hormonal male contraceptive regimens generally achieve only incomplete suppression to azoospermia with potentially adverse metabolic effects. We have carried out a short-term dose-finding study to investigate the potential of an oral gestogen, desogestrel, with testosterone pellets. Normal men received a single dose of 300 mg testosterone with 75 microg, 150 microg or 300 microg desogestrel daily for 8 weeks (n = 10 per group). LH and FSH were rapidly suppressed, with little difference between groups. Testosterone concentrations fell slightly during treatment with evidence of a linear dosage effect. Plasma inhibin B showed minor changes, but in seminal plasma it was suppressed, becoming undetectable in all men in the 300 microg desogestrel group. There were no significant changes in lipoproteins, fibrinogen or sexual behaviour during treatment, and minor falls in haematocrit and haemoglobin concentration. Sperm concentration fell in a dose-dependent manner, with three men, one man and seven men in the three groups respectively achieving severe oligozoospermia (<3 x 10(6)/ml), and three men achieving azoospermia in the 300 microg group despite the short duration of the study. The combination of oral desogestrel with depot testosterone thus results in profound suppression of gonadotrophin secretion without adverse metabolic or behavioural effects. Desogestrel with a long-acting testosterone preparation is a promising approach to hormonal male contraception.

Hormone substitution in male hypogonadism

Male hypogonadism is characterised by androgen deficiency and infertility. Hypogonadism can be caused by disorders at the hypothalamic or pituitary level (hypogonadotropic forms) or by testicular dysfunction (hypergonadotropic forms). Testosterone substitution is necessary in all hypogonadal patients, because androgen deficiency causes slight anemia, changes in coagulation parameters, decreased bone density, muscle atrophy, regression of sexual function and alterations in mood and cognitive abilities. Androgen replacement comprises injectable forms of testosterone as well as implants, transdermal systems, sublingual, buccal and oral preparations. Transdermal systems provide the pharmacokinetic modality closest to natural diurnal variations in testosterone levels. New injectable forms of testosterone are currently under clinical evaluation (testosterone undecanoate, testosterone buciclate), allowing extended injection intervals. If patients with hypogonadotropic hypogonadism wish to father a child, spermatogenesis can be initiated and maintained by gonadotropin therapy (conventionally in the form of human chorionic gonadotropin (hCG) and human menopausal gonadotropin (hMG) or, more recently, purified or recombinant follicle stimulating hormone (FSH)). Apart from this option, patients with disorders at the hypothalamic level can be stimulated with pulsatile gonadotropin-releasing hormone (GnRH). Both treatment modalities have to be administered on average for 7-10 months until pregnancy is achieved. In individual cases, treatment may be necessary for up to 46 months. Testosterone treatment is interrupted for the time of GnRH of gonadotropin therapy, but resumed after cessation of this therapy.

Castration increases and androgens decrease nitric oxide synthase activity in the brain: physiologic implications

Sex differences in nitric oxide synthase (NOS) activity in different regions of the rat brain and effects of testosterone and dihydrotestosterone (DHT) treatment in orchidectomized animals were investigated. Regional but no sex differences in NOS activity were detected in gonadectomized animals. Orchidectomy significantly increased NOS activity in the hypothalamus, "amygdala," and cerebellum but not in the cortex. In the hypothalamus, the increase in NOS activity after castration and its reversal by androgen treatment was mimicked by changes in neuronal NOS mRNA level. In contrast, androgen receptor (AR) mRNA level in the hypothalamus was slightly reduced by castration and increased by treatment with DHT. Again in the hypothalamus, the increase in NOS activity in castrated rats was accompanied by an increase in the number of neuronal NOS+ cells determined immunohistochemically, whereas androgen treatment prevented this increase. The changes in NOS+ neurons correlated with the changes in the number of AR+ cells to a degree. Overlap of AR in NOS+ cells was not present in the regions of the hypothalamus analyzed. These results indicate that testosterone or, most likely, its metabolite DHT down-regulates NOS activity, mRNA expression or stabilization, and the number of neuronal NOS+ neurons.

Castration increases and androgens decrease nitric oxide synthase activity in the brain: Physiologic implications

Sex differences in nitric oxide synthase (NOS) activity in different regions of the rat brain and effects of testosterone and dihydrotestosterone (DHT) treatment in orchidectomized animals were investigated. Regional but no sex differences in NOS activity were detected in gonadectomized animals. Orchidectomy significantly increased NOS activity in the hypothalamus, "amygdala," and cerebellum but not in the cortex. In the hypothalamus, the increase in NOS activity after castration and its reversal by androgen treatment was mimicked by changes in neuronal NOS mRNA level. In contrast, androgen receptor (AR) mRNA level in the hypothalamus was slightly reduced by castration and increased by treatment with DHT. Again in the hypothalamus, the increase in NOS activity in castrated rats was accompanied by an increase in the number of neuronal NOS+ cells determined immunohistochemically, whereas androgen treatment prevented this increase. The changes in NOS+ neurons correlated with the changes in the number of AR+ cells to a degree. Overlap of AR in NOS+ cells was not present in the regions of the hypothalamus analyzed. These results indicate that testosterone or, most likely, its metabolite DHT down-regulates NOS activity, mRNA expression or stabilization, and the number of neuronal NOS+ neurons.

Repeated intramuscular injections of testosterone undecanoate for substitution therapy in hypogonadal men

OBJECTIVE

To investigate the suitability of intramuscular testosterone undecanoate (TU) injections for substitution therapy in hypogonadal men.

STUDY DESIGN

Clinical, open-label, non-randomized trial of 13 hypogonadal men receiving 4 intramuscular injections of 1000 mg TU in 4-ml castor oil at 6-week intervals. General wellbeing, sexual parameters, clinical chemistry, hormone levels, prostate size and prostate-specific antigen (PSA) were evaluated over 24 weeks and compared with baseline values.

RESULTS

Testosterone serum levels were never found below the lower limit of normal and only briefly after the 3rd and 4th injection above the upper limit of normal, while peak and trough values increased over the 24-week observation period. Oestradiol and dihydrotestosterone followed this pattern, not exceeding the normal limits. No serious side-effects were noted. Slight increases in body weight, haemoglobin, haematocrit, prostate volume and PSA, suppression of gonadotrophins as well as increased ejaculation frequency occurred as signs of adequate testosterone substitution.

CONCLUSION

Testosterone undecanoate is well tolerated by the patients. The injection intervals can be extended even beyond the 6-week periods chosen in the present study. Altogether, intramuscular testosterone undecanoate appears to be well suited for long-term substitution therapy in hypogonadism and hormonal male contraception.

Influence of various modes of androgen substitution on serum lipids and lipoproteins in hypogonadal men

We investigated whether the androgen type or application mode or testosterone (T) serum levels influence serum lipids and lipoprotein levels differentially in 55 hypogonadal men randomly assigned to the following treatment groups: mesterolone 100 mg orally daily ([MES] n = 12), testosterone undecanoate 160 mg orally daily ([TU] n = 13), testosterone enanthate 250 mg intramuscularly every 21 days ([TE] n = 15), or a single subcutaneous implantation of crystalline T 1,200 mg ([TPEL] n = 15). The dosages were based on standard treatment regimens. Previous androgen substitution was suspended for at least 3 months. Only metabolically healthy men with serum T less than 3.6 nmol/L and total cholesterol (TC) and triglyceride (TG) less than 200 mg/dL were included. After a screening period of 2 weeks, the study medication was taken from days 0 to 189, with follow-up visits on days 246 and 300. Before substitution, all men were clearly hypogonadal, with mean serum T less than 3 nmol/L in all groups. Androgen substitution led to no significant increase of serum T in the MES group, subnormal T in the TU group (5.7 +/- 0.3 nmol/L), normal T in the TE group (13.5 +/- 0.7 nmol/L), and high-normal T in the TPEL group (23.2 +/- 1.1 nmol/L). 5 alpha-Dihydrotestosterone significantly increased in all treatment groups compared with baseline. Compared with presubstitution levels, a significant increase of TC was observed in all treatment groups (TU, 14.4% +/- 3.0%; MES, 18.8% +/- 2.5%; TE, 20.4% +/- 3.0%; TPEL, 20.2% +/- 2.6%). Low-density lipoprotein cholesterol (LDL-C) also increased significantly by 34.3% +/- 5.5% (TU), 46.4% +/- 4.1% (MES), 65.2% +/- 5.7% (TE), and 47.5% +/- 4.3% (TPEL). High-density lipoprotein cholesterol (HDL-C) showed a significant decrease by -30.9% +/- 2.8% (TU), -34.9% +/- 2.5% (MES), -35.7% +/- 2.6% (TE), and -32.5% +/- 3.5% (TPEL). Serum TG significantly increased by 37.3% +/- 11.3% (TU), 46.4% +/- 10.3% (MES), 29.4% +/- 6.5% (TE), and 22.9% +/- 6.7% (TPEL). TU caused a smaller increase of TC than TE and TPEL, whereas the parenteral treatment modes showed a lower increase of TG. There was no correlation between serum T and lipid concentrations. Despite the return of serum T to pretreatment levels, serum lipid and lipoprotein levels did not return to baseline during follow-up evaluation. In summary, androgen substitution in hypogonadal men increases TC, LDL-C, and TG and decreases HDL-C independently of the androgen type and application made and the serum androgen levels achieved. Due to the extended washout period for previous androgen medication and the exclusion of men with preexisting hyperlipidemia, this investigation demonstrates more clearly than previous studies the impact of androgen effects on serum lipids and lipoproteins. It is concluded that preexisting low serum androgens induce a "male-type" serum lipid profile, and increasing serum androgens further within the male normal range does not exert any additional effects. The threshold appears to be above the normal female androgen serum levels and far below the lower limit of normal serum T levels in adult men. These findings may have considerable implications for the use of androgens as a male contraceptive and for androgen therapy in elderly men.

Testosterone replacement therapy

The benefits conferred by testosterone replacement therapy are substantial, both in the short term for the eradication of symptoms of androgen deficiency, and in the long term for the prevention of osteoporosis. As with any long-term treatment there are risks that must be considered, but overall the benefits achieved far outweigh potential risk. Ideally, androgen replacement therapy should provide physiological serum testosterone levels, as well as DHT and estradiol levels, and correct the clinical symptoms of androgen deficiency in hypogonadal men. This goal is difficult to achieve because the dose dependency of androgen-dependent physiological processes is not known. Androgen preparations that are currently available do not fulfill all criteria for an ideal androgen replacement therapy. Parenteral testosterone esters are effective, safe, practical, and inexpensive. The transdermal testosterone systems provide an alternative to testosterone esters in selected patients but these preparations are expensive. Ongoing studies are showing the benefits of testosterone replacement therapy in aging men, but there is concern about side effects on cardiovascular system and prostate. Thus, clinical decision regarding testosterone therapy in older men should be better defined.