Effects of oral testosterone undecanoate in hypogonadal male patients

Oral testosterone therapy: past, present, and future

INTRODUCTION

Testosterone replacement therapy (TRT) remains a commonly utilized treatment for men with testosterone deficiency (TD). Despite the recent FDA approval of new oral TRT medications, concerns remain regarding their efficacy and safety, and prescription rates for these medications have decreased compared to those for TD medications with other routes of administration.

OBJECTIVE

In this study we sought to investigate the efficacy and safety of oral testosterone undecanoate (oTU), a new oral TRT medication.

METHODS

A comprehensive review of the literature was performed using the Medline, EMBASE, and Cochrane Library databases; 1269 articles were identified, with 44 articles included in the final review and 12 used to perform meta-analyses to investigate the change in serum total testosterone (TT) and risk of adverse effects following oral testosterone undecanoate (oTU) use. Articles were also reviewed to investigate the reported effects of oTU on body composition, liver function, hematologic assays, lipid profiles, hormone assays, prostate growth, hypertension, and symptoms of TD.

RESULTS

Across placebo-controlled randomized trials, there was no significant increase in TT for those receiving oTU vs placebo (mean difference, -0.26 [95% CI, -1.26 to 0.73]). On subanalysis, when eugonadal participants received oTU, a significant decrease in TT was demonstrated (mean difference -0.86 [95% CI, -1.28 to 0.43]). When participants who were hypogonadal at baseline received oTU, a significant increase in TT compared to placebo was seen (mean difference 1.25 [95% CI, 0.22-2.29]). There was no significant risk of adverse effects (RR, -0.03 [95% CI, -0.08 to 0.03]) or serious adverse effects (RR, 0.15 [95% CI, -0.66 to 0.96]) in the oTU groups compared to placebo.

CONCLUSION

oTU was found to be well tolerated in hypogonadal patients, resulting in improved testosterone levels, height velocity, and sexual symptoms, without significant hepatotoxicity, prostatic enlargement, or worsening hypertension. There was no consensus regarding the effect of oTU on lean and fat mass percentages, hematologic assays, lipid profiles, mood, and general well-being.

Quantitative characterization of UDP-glucuronosyltransferase 2B17 in human liver and intestine and its role in testosterone first-pass metabolism

Protein abundance and activity of UGT2B17, a highly variable drug- and androgen-metabolizing enzyme, were quantified in microsomes, S9 fractions, and primary cells isolated from human liver and intestine by validated LC-MS/MS methods. UGT2B17 protein abundance showed >160-fold variation (mean ± SD, 1.7 ± 2.7 pmol/mg microsomal protein) in adult human liver microsomes (n = 26) and significant correlation (r2 = 0.77, p < 0.001) with testosterone glucuronide (TG) formation. Primary role of UGT2B17 in TG formation compared to UGT2B15 was confirmed by performing activity assays in UGT2B17 gene deletion samples and with a selective UGT2B17 inhibitor, imatinib. Human intestinal microsomes isolated from small intestine (n = 6) showed on average significantly higher protein abundance (7.4 ± 6.6 pmol/mg microsomal protein, p = 0.016) compared to liver microsomes, with an increasing trend towards distal segments of the gastrointestinal (GI) tract. Commercially available pooled microsomes and S9 fractions confirmed greater abundance and activity of UGT2B17 in intestinal fractions compared to liver fractions. To further investigate the quantitative role of UGT2B17 in testosterone metabolism in whole cell system, a targeted metabolomics study was performed in hepatocytes (n = 5) and enterocytes (n = 16). TG was the second most abundant metabolite after androstenedione in both cell systems. Reasonable correlation between UGT2B17 abundance and activity were observed in enterocytes (r2 = 0.69, p = 0.003), but not in hepatocytes. These observational and mechanistic data will be useful in developing physiologically-based pharmacokinetic (PBPK) models for predicting highly-variable first-pass metabolism of testosterone and other UGT2B17 substrates.

Cardiovascular risks and elevation of serum DHT vary by route of testosterone administration: a systematic review and meta-analysis

BACKGROUND

Potential cardiovascular (CV) risks of testosterone replacement therapy (TRT) are currently a topic of intense interest. However, no studies have addressed CV risk as a function of the route of administration of TRT.

METHODS

Two meta-analyses were conducted, one of CV adverse events (AEs) in 35 randomized controlled trials (RCTs) of TRT lasting 12 weeks or more, and one of 32 studies reporting the effect of TRT on serum testosterone and dihydrotestosterone (DHT).

RESULTS

CV risks of TRT: Of 2,313 studies identified, 35 were eligible and included 3,703 mostly older men who experienced 218 CV-related AEs. No significant risk for CV AEs was present when all TRT administration routes were grouped (relative risk (RR) = 1.28, 95% confidence interval (CI): 0.76 to 2.13, P = 0.34). When analyzed separately, oral TRT produced significant CV risk (RR = 2.20, 95% CI: 1.45 to 3.55, P = 0.015), while neither intramuscular (RR = 0.66, 95% CI: 0.28 to 1.56, P = 0.32) nor transdermal (gel or patch) TRT (RR = 1.27, 95% CI: 0.62 to 2.62, P = 0.48) significantly altered CV risk. Serum testosterone/DHT following TRT: Of 419 studies identified, 32 were eligible which included 1,152 men receiving TRT. No significant difference in the elevation of serum testosterone was present between intramuscular or transdermal TRT. However, transdermal TRT elevated serum DHT (5.46-fold, 95% CI: 4.51 to 6.60) to a greater magnitude than intramuscular TRT (2.20-fold, 95% CI: 1.74 to 2.77).

CONCLUSIONS

Oral TRT produces significant CV risk. While no significant effects on CV risk were observed with either injected or transdermal TRT, the point estimates suggest that further research is needed to establish whether administration by these routes is protective or detrimental, respectively. Differences in the degree to which serum DHT is elevated may underlie the varying CV risk by TRT administration route, as elevated serum dihydrotestosterone has been shown to be associated with CV risk in observational studies.

Testosterone, Thrombophilia, and Thrombosis

We describe thrombosis, deep venous thrombosis (DVT) pulmonary embolism (PE; n = 9) and hip-knee osteonecrosis (n = 5) that developed after testosterone therapy (median 11 months) in 14 previously healthy patients (13 men and 1 woman; 13 Caucasian and 1 African American), with no antecedent thrombosis and previously undiagnosed thrombophilia–hypofibrinolysis. Of the 14 patients, 3 were found to be factor V Leiden heterozygotes, 3 had high factor VIII, 3 had plasminogen activator inhibitor 1 4G4G homozygosity, 2 had high factor XI, 2 had high homocysteine, 1 had low antithrombin III, 1 had the lupus anticoagulant, 1 had high anticardiolipin antibody Immunoglobulin G, and 1 had no clotting abnormalities. In 4 men with thrombophilia, DVT-PE recurred when testosterone was continued despite therapeutic international normalized ratio on warfarin. In 60 men on testosterone, 20 (33%) had high estradiol (E2 >42.6 pg/mL). When exogenous testosterone is aromatized to E2, and E2-induced thrombophilia is superimposed on thrombophilia–hypofibrinolysis, thrombosis occurs. The DVT-PE and osteonecrosis after starting testosterone are associated with previously undiagnosed thrombophilia–hypofibrinolysis. Thrombophilia should be ruled out before administration of exogenous testosterone.

Pharmacokinetics of modified slow-release oral testosterone over 9 days in normal men with experimental hypogonadism

Oral administration of testosterone has potential use for the treatment of hypogonadism. We have recently demonstrated that a novel formulation of oral testosterone transiently normalized serum testosterone in a single-dose pharmacokinetic study. In this report, we present the steady-state pharmacokinetics of this formulation. Twelve healthy young men were rendered hypogonadal with the gonadotropin-releasing hormone antagonist acyline (300 μg/kg subcutaneously) and administered 300 mg of oral testosterone 3 times daily for 9 days. Serum testosterone, dihydrotestosterone (DHT), estradiol, and sex hormone-binding globulin (SHBG) were measured before and 1, 2, 4, 5, 6, 8, 10, 11, 12, 14, 16, and 24 hours on the first and ninth day of dosing. Before testosterone administration, all men had serum testosterone under 75 ng/dL. Over day 1, the 24-hour average (geometric mean [%CV]) serum total testosterone was 378 (45) ng/dL. This decreased to 315 (41) ng/dL after 9 days of continuous treatment (P = .1 compared with day 1). The 24-hour average serum SHBG was 27 (46) nmol/L on day 1 and was significantly reduced to 19 (47) nmol/L by day 9 (P < .01). As a result, the calculated free testosterone values were similar between day 1 and day 9: 8.7 (43) and 8.3 (37) ng/dL, respectively. DHT was in the reference range and estradiol was slightly below on day 9. Oral testosterone (300 mg) dosed 3 times daily normalized serum testosterone in men with experimentally induced hypogonadism after 9 days of dosing and significantly suppressed SHBG. This formulation of oral testosterone may have efficacy for the treatment of testosterone deficiency.

Steady-state pharmacokinetics of oral testosterone undecanoate with concomitant inhibition of 5α-reductase by finasteride

Oral testosterone undecanoate (TU) is used to treat testosterone deficiency; however, oral TU treatment elevates dihydrotestosterone (DHT), which may be associated with an increased risk of acne, male pattern baldness and prostate hyperplasia. Co-administration of 5α-reductase inhibitors with other formulations of oral testosterone suppresses DHT production and increases serum testosterone. We hypothesized that finasteride would increase serum testosterone and lower DHT during treatment with oral TU. Therefore, we studied the steady-state pharmacokinetics of oral TU, 200 mg equivalents of testosterone twice daily for 7 days, alone and with finasteride 0.5 and 1.0 mg po twice daily in an open-label, three-way crossover study in 11 young men with experimentally induced hypogonadism. On the seventh day of each dosing period, serum testosterone, DHT and oestradiol were measured at baseline and 1, 2, 4, 8, 12, 13, 14, 16, 20 and 24 h after the morning dose. Serum testosterone and DHT were significantly increased into and above their normal ranges similarly by all three treatments. Co-administration of finasteride at 0.5 and 1.0 mg po twice daily had no significant effect on either serum testosterone or DHT. Oral TU differs from other formulations of oral testosterone in its response to concomitant inhibition of 5α-reductase, perhaps because of its unique lymphatic route of absorption.

Biochemical endocrinology of the hypogonadal male

Hypogonadism in the male results from inadequate testicular function, especially defects in androgen synthesis and secretion, or action. Androgen action is important throughout normal male development: in the fetus, puberty, adult life and old age. Regulation is by variable activity of the hypothalamo-pituitary axis at different phases of the life span. Clinical aspects include: genetic aspects presenting at birth and pubertal failure/arrest. Aspects in adult life embrace sexuality, somatic symptoms and osteoporosis. Acquired causes of hypogonadism may arise from various forms of testicular damage (primary hypogonadism), pituitary and hypothalamic disorders, as well as aetiologies acting at several sites. Measurement of testosterone (T) is crucial to the diagnosis of hypogonadism and the technologies continue to develop, with recent major advances. A growing problem relates to the diagnosis and treatment of hypogonadism in the ageing male. T therapy is available in several forms, with major improvements in more newly available modalities.

Pharmacokinetics of 2 novel formulations of modified-release oral testosterone alone and with finasteride in normal men with experimental hypogonadism

Oral administration of testosterone might be useful for the treatment of testosterone deficiency. However, current "immediate-release" formulations of oral testosterone exhibit suboptimal pharmacokinetics, with supraphysiologic peaks of testosterone and its metabolite, dihydrotestosterone (DHT), immediately after dosing. To dampen these peaks, we have developed 2 novel modified-release formulations of oral testosterone designed to slow absorption from the gut and improve hormone delivery. We studied these testosterone formulations in 16 normal young men enrolled in a 2-arm, open-label clinical trial. Three hundred-mg and 600-mg doses of immediate-release and modified fast-release or slow-release formulations were administered sequentially to 8 normal men rendered hypogonadal by the administration of the gonadotropin-releasing hormone antagonist acyline. Blood for measurement of serum testosterone, DHT, and estradiol was obtained before and 0.5, 1, 2, 3, 4, 6, 8, 12, and 24 hours after each dose. A second group of 8 men was studied with the coadministration of 1 mg of the 5α-reductase inhibitor finasteride daily throughout the treatment period. Serum testosterone was increased with all formulations of oral testosterone. The modified slow-release formulation significantly delayed the postdose peaks of serum testosterone and reduced peak concentrations of serum DHT compared with the immediate-release formulation. The addition of finasteride further increased serum testosterone and decreased serum DHT. We conclude that the oral modified slow-release testosterone formulation exhibits superior pharmacokinetics compared with immediate-release oral testosterone both alone and in combination with finasteride. This formulation might have efficacy for the treatment of testosterone deficiency.

Comparison of oral versus transdermal testosterone supplementation in hypogonadal men

: To compare mean serum total testosterone, bioavailable-testosterone, and dihydrotestosterone levels between transdermal testosterone and oral testosterone undecanoate treatment.

: Multicentre, randomized, cross-over study; 44 men >18 years, testosterone ≤2.5 ng/mL. Two patches (Testopatch

: Mean age 49 years. Mean testosterone before inclusion 1.99 ng/mL. Mean testosterone serum levels over the last 48 h of Testopatch treatment were superior to Pantestone (4.64 vs. 2.58 ng/mL, p<0.001). Testosterone trough levels at the end of each treatment period were significantly higher for Testopatch (3.15 vs. 2.45 ng/mL, p<0.01). Bioavailable-testosterone levels over the first and last 48 h of treatment were significantly greater with Testopatch than with Pantestone (p=0.001 and p<0.01). Dihydrotestosterone levels over the first and last 48 h of treatment (0.71 vs. 1.05 ng/mL and 0.68 vs. 0.89 ng/mL) as well as at trough (0.59 vs. 0.96 ng/mL) were significantly lower with Testopatch than with Pantestone (p<0.001, p<0.05, and p<0.001). SHBG levels decreased by Pantestone but not by Testopatch (p<0.001).

: Testopatch was superior to Pantestone to increase testosterone and bioavailable-testosterone levels in hypogonadal men from the first days and throughout the three weeks of treatment. Pantestone increased dihydrotestosterone to a larger extent and decreased SHBG.

Pharmacokinetics and pharmacodynamics of subcutaneous testosterone implants in hypogonadal men

OBJECTIVE

There are advantages and disadvantages with all of the presently available types of testosterone replacement for hypogonadal men. We performed this investigation to establish detailed data about the pharmacokinetics, pharmacodynamics, feasibility and side-effects of subcutaneously implanted testosterone (T) pellets.

DESIGN AND MEASUREMENT

In a single-dose, open-label, non-randomized study, 6 T-pellets, each containing 200 mg of fused crystalline T, were implanted in the subdermal fat tissue of the lower abdominal wall of 14 hypogonadal men. Blood samples for determination of T, LH, FSH, 5 alpha-dihydrotestosterone (DHT), sex hormone binding globulin (SHBG) and oestradiol (E2) were obtained at 0, 0.5, 1, 2, 4, 8, 12, 24, 36, 48 hours and on day 21 after implantation and then every 3 weeks until day 189, and on days 246 and 300 during follow-up. In another 36 hypogonadal men the feasibility and side-effects of T-pellets were evaluated.

PATIENTS

Fourteen patients participated in the detailed pharmacokinetic study and another 36 patients in the assessment of feasibility and side-effects. All patients (age range 18-61 years) suffered from primary or secondary hypogonadism (T < 3.6 nmol/l).

RESULTS

The pharmacokinetic study in 14 hypogonadal men revealed an initial short-lived burst release of T with a peak concentration of 49.0 +/- 3.7 nmol/l at 0.5 +/- 0.13 days which was followed by a stable plateau lasting until day 63 (day 2, 35.2 +/- 2.3; day 63, 34.8 +/- 2.6 nmol/l). Thereafter serum T gradually declined and was close to baseline concentrations on day 300. Apparent terminal elimination half-life (t1/2) was 70.8 +/- 10.7 days and apparent mean residence time 87.0 +/- 4.5 days. On average, serum T was below 10 nmol/l after 180 days. Absorption of T followed a zero-order release kinetic with an absorption half-time of 74.7 days (95% confidence interval: 71.1-78.5) and was almost complete by day 189 (95.9 +/- 0.84%). Serum DHT and E2 were significantly elevated from day 21 to day 105 and correlated significantly with T (DHT, r = 0.65, P < 0.0001, E2, r = 0.67, P < 0.0001). SHBG was significantly decreased from day 21 to day 168. In 6 men with primary hypogonadism T suppressed LH and FSH to the eugonadal range from day 21 to 126 and 42 to 105, respectively, with nadirs occurring at day 84 (LH) and day 63 (FSH). LH and FSH were highly inversely correlated with T (r = -0.47 and -0.57). The only side-effect observed during 112 implantations in the total group of 50 men were 6 local infections (5.4%) leading to extrusion of 5 pellets in 3 men. When given the choice, all patients except one preferred T-pellets to their previous T medication for permanent substitution therapy.

CONCLUSION

T-pellets are the androgen formulation with the longest biological action and strongest pharmacodynamic efficacy in terms of gonadotrophin suppression. The pharmacokinetic features are advantageous compared to other T preparations and the patient acceptance is high.

Aggression in humans: what is its biological foundation?

Although human aggression is frequently inferred to parallel aggression based on testosterone in nonprimate mammals, there is little concrete support for this position. High- and low-aggression individuals do not consistently differ in serum testosterone. Aggression does not change at puberty when testosterone levels increase. Aggression does not increase in hypogonadal males (or females) when exogenous testosterone is administered to support sexual activity. Similarly, there are no reports that aggression increases in hirsute females even though testosterone levels may rise to 200% above normal. Conversely, castration or antiandrogen administration to human males is not associated with a consistent decrease in aggression. Finally, changes in human aggression associated with neuropathology are not consistent with current knowledge of the neural basis of testosterone-dependent aggression. In contrast, human aggression does have a substantial number of features in common with defensive aggression seen in nonprimate mammals. It is present at all age levels, is displayed by both males and females, is directed at both males and females, and is not dependent on seasonal changes in hormone levels or experiential events such as sexual activity. As would be expected from current knowledge of the neural system controlling defensive aggression, aggression in humans increases with tumors in the medial hypothalamus and septal region, and with seizure activity in the amygdala. It decreases with lesions in the amygdala. The inference that human aggression has its roots in the defensive aggression of nonprimate mammals is in general agreement with evidence on the consistency of human aggressiveness over age, with similarities in male and female aggressiveness in laboratory studies, and with observations that some neurological disturbances contribute to criminal violence. This evidence suggests that human aggression has its biological roots in the defensive aggression of nonprimate mammals and not in hormone-dependent aggression based on testosterone.

Effects of oral testosterone undecanoate on growth, body composition, strength and energy expenditure of adolescent boys

OBJECTIVE

We determined the effect of 3 months of daily, 40 mg oral testosterone undecanoate on growth, body composition, hand grip and quadriceps muscle strength, and total free-living daily energy expenditure in boys with constitutionally delayed puberty.

DESIGN

Double blind, placebo controlled study.

PATIENTS

Eighteen boys with constitutionally delayed puberty, mean (SD) age 13.2 (1.6) years.

MEASUREMENTS

Body composition measurements were made by skinfold thickness, bioelectrical impedance and stable isotope dilution (H2(18)O) methods. Energy expenditure was assessed by the doubly-labelled water (2H2(18)O) technique.

RESULTS

Height velocity increased from 5.4 (0.8) to 8.1 (0.6) cm/year (P < 0.05) in the 3 months after active therapy. Fat-free mass increased more with therapy (2.7 (0.3) kg) over the 6-month study period than with placebo (1.7 (0.4) kg, P < 0.5). Height velocity increases correlated with daily increases in fat-free mass (r = 0.68, P = 0.005) in the study group as a whole. Energy expenditure and muscle strength increased similarly in both groups. Predicted adult height decreased in the group which was treated with testosterone undecanoate.

CONCLUSIONS

Testosterone undecanoate (40 mg daily for 3 months) significantly increased height velocity and fat-free mass velocities after 6 months but not muscle strength, endurance or total daily energy expenditure.

Radioimmunoassay of 7 alpha-methyl-19-nortestosterone and investigation of its pharmacokinetics in animals

A method for the measurement of 7 alpha-methyl-19-nortestosterone (7MENT) in serum/plasma by radioimmunoassay (RIA) is described. The antiserum, raised against 7 alpha-methyl-19-nortestosterone-3-O-oxime-bovine serum albumin, had a low titer (final dilution = 1:4500) and low affinity (Ka = 1.17 x 10(9) l/mol) but showed little or no cross-reactivity with several of the steroids tested. The sensitivity of the RIA was 28.2 pg/ml and the mean recovery of added cold steroid was 86 to 100%. Intra- and inter-assay coefficients of variation ranged from 4.3 to 7.3% and 7.3 to 8.4%, respectively. This RIA was used to follow plasma 7MENT levels after a single i.v. injection of the steroid in rats and rabbits. The metabolic clearance rates (MCR) of 7MENT as determined from the plasma disappearance curve for rats and rabbits were 50 l/day and 336 l/day, respectively. The MCR of 7MENT in rats and rabbits lies in the same range as for testosterone. When compared to other nortestosterone derivatives such as norethisterone, 7MENT is metabolized relatively faster.

Sexual behavior of men with isolated hypogonadotropic hypogonadism or prepubertal anterior panhypopituitarism

Sexual behavior of men with secondary hypogonadism was studied. Seven of the thirteen subjects presented with hypogonadism secondary to isolated gonadotropin (Gn) deficit, whereas the other six had idiopathic prepubertal anterior panhypopituitarism. Testosterone (T) levels were low and did not differ between the two groups. All subjects were evaluated both during replacement therapy (Gn in the first group; Gn plus cortisone and thyroxine in the second group) and 2 months after withdrawal of Gn therapy. During and after withdrawal of Gn administration, men with isolated deficit of Gn retained sexual activity and nocturnal penile tumescence, although they were partially compromised compared with a control group; on the other hand, panhypopituitarics reported compromised sexual function during Gn treatment and no sexual function when Gn therapy was not given. We conclude that different lesions of the hypothalamus-pituitary axis were accompanied by varying degrees of sexual impairment in the two groups of men presenting both secondary hypogonadism and very low T levels.

Inhibition of spermatogenesis in men using various combinations of oral progestagens and percutaneous or oral androgens

Eight men (experiment 1) requesting male contraception received a daily oral dose of 20 mg medroxyprogesterone acetate (MPA) combined with 125 mg percutaneous dihydrotestosterone (DHT). Three months later the mean sperm count was only diminished slightly; the replacement of DHT for four men by percutaneous testosterone at the same concentration led to a dramatic fall in sperm count. For 6-18 months all men were treated with MPA plus percutaneous testosterone (250 mg daily). The latter dose restored physiological levels of plasma testosterone. Follicle-stimulating hormone levels were inhibited more severely than in the DHT-treated group, whereas LH levels were variable. Azoospermia was achieved and maintained in six cases; two men were oligozoospermic and in one case a moderate secondary rise in the sperm count was observed. Twelve volunteers (experiment 2) received a daily oral dose of either 5 or 10 mg norethisterone acetate plus percutaneous testosterone (250 mg daily). All of them achieved azoospermia within 2 months, but two subjects later exhibited a partial restoration in sperm count. Follicle-stimulating hormone and LH levels were inhibited more severely than in the first experiment. The sperm count and gonadotrophin levels returned to initial values within 6 months after cessation of the treatment in both experiments. No side-effects were noted concerning blood parameters, libido or body weight. However, several female partners had elevated levels of plasma testosterone. In experiment 3 (13 volunteers), percutaneous testosterone was replaced by oral testosterone undecanoate (160 mg daily). Only seven men were azoospermic and most of them had lowered levels of plasma testosterone. Thus, the combination of percutaneous testosterone and oral progestagens appears to be the most convenient for male hormonal contraception.

Long-term safety of the oral androgen testosterone undecanoate

In 35 men treated with testosterone undecanoate (TU) at a dosage of 80-200 mg/day, liver function was measured every 6 months for a period of 72 months. None of the parameters changed. In 8 subjects of 50-62 years of age upon starting this type of treatment, urine flow was not found to decrease over the test period of 72 months. Also other signs of benign prostatic hypertrophy were not reported. In 9 subjects for whom TU was the first type of androgen treatment, no signs of gynaecomastia were found during the first 6 months of the therapy or later. These data provide evidence that TU is a reasonably safe form of oral androgen therapy.

Failure of high-dose sustained release luteinizing hormone releasing hormone agonist (buserelin) plus oral testosterone to suppress male fertility

Previously we have demonstrated that sperm counts of normal young men decreased during constant subcutaneous infusion of the LHRH agonist buserelin (118 or 230 micrograms/d). In order to test whether azoospermia can be achieved with higher doses, seven young men received 450 micrograms buserelin subcutaneously daily for 12 weeks via extracorporeal osmotic minipumps. To avoid symptoms of androgen deficiency, oral supplementation with 80 mg/d testosterone undecanoate (TU) was initiated in week 5 and was increased to 120 mg/d by week 8. Follow-up after treatment lasted for another 12 weeks. In order to evaluate possible psychotropic effects of treatment-related endocrine changes, continuous psychometric testing was performed focusing on personality, emotions and sexuality. After an initial rise, both serum LH and FSH returned to normal. FSH was below normal during the 3rd-5th week following treatment. LHRH stimulation tests performed at the end of treatment showed pituitary desensitization. Serum T (always measured between 0800 and 1300 h at least 12 h after last TU) tended to decrease by week 7 and remained slightly depressed until the end of treatment while libido, potency and emotional well-being remained unchanged. While testicular volumes showed a reduction from week 7 of treatment to week 10 post-treatment, sperm counts decreased only insignificantly from 65 +/- 10 to 44 +/- 14 million per ml in week 12 post-treatment. Severe oligo- or azoospermia was not observed in any of the seven men. It is concluded that full androgen substitution by TU can drastically delay if not abolish the antifertility effect of LHRH-induced pituitary desensitization.

High dose androgen therapy in male pseudohermaphroditism due to 5 alpha-reductase deficiency and disorders of the androgen receptor

We describe the clinical and biochemical features of six men with male pseudohermaphroditism due to androgen resistance. Each of the subjects had male-gender behavior but incomplete virilization. The underlying defects in androgen metabolism were defined by studies of the 5 alpha-reductase enzyme and the androgen receptor in fibroblasts cultured from biopsies of genital skin. Four of the six have 5 alpha-reductase deficiency, and two have defects of the androgen receptor (the Reifenstein syndrome). The responses of these men to androgen treatment were assessed by monitoring nitrogen balance, plasma luteinizing hormone (LH) values, and clinical parameters of virilization including penile growth, potency and ejaculatory volume, muscle bulk, and growth of body and facial hair. In all of the subjects with 5 alpha-reductase deficiency and one man with the Reifenstein syndrome significant response occurred, as evidence by nitrogen retention, lowered plasma LH levels, and improved virilization, with doses of parenteral testosterone esters that raised plasma testosterone levels above the normal male range and brought plasma dihydrotestosterone levels into the normal male range. The subject who did not respond with clinical virilization nevertheless showed nitrogen retention in response to acute testosterone administration. This patient had a profound deficiency of the androgen receptor, whereas the man with a receptor defect who did respond clinically to therapy had normal amounts of a qualitatively abnormal receptor. We conclude that high dose androgen therapy may be of benefit in improving virilization, self-image, and sexual performance in subjects with 5 alpha-reductase deficiency who have male-gender behavior and in some subjects with defects of the androgen receptor.

Which testosterone replacement therapy?

Three different forms of testosterone (T) replacement therapy were compared; they were the intramuscular injection of mixed testosterone esters 250 mg; the subcutaneous implantation of 6 X 100 mg pellets of fused testosterone; and the oral administration of testosterone undecanoate (TU) 80 mg twice daily. Six hypogonadal males were treated with oral TU for an eight week period, during which time serial serum hormonal estimations were performed over 10 h at the initiation and after four and eight weeks of therapy. Serum T levels showed marked variability both between subjects and within the same subject on different occasions. We attribute this to variability in absorption of TU, which is formulated in oleic acid. The overall mean T level calculated from the areas under the profiles of TU was 12.0 nmol/l. Hormone responses to injected T esters were studied in nine hypogonadal males. Serum T rose to supraphysiological peak concentrations (mean 71 nmol/l) 24-48 h after an injection, followed by an exponential decay to reach baseline concentrations after 2-3 weeks. The overall calculated mean T level in subjects receiving testosterone esters 250 mg every three weeks was 27.7 nmol/l. Subcutaneous implantation of testosterone in six hypogonadal men produced a gradual rise in serum T followed by a slow decline, with T levels remaining within the normal range for 4-5 months. The calculated overall mean T level over 21 weeks after implantation was 17.0 nmol/l. Serum oestradiol (E2) levels remained within the normal male range throughout the study periods on both TU and T implant therapy but showed a supraphysiological peak (mean 347 pmol/l) 24-48 h after a T injection. 5 alpha-dihydrotestosterone (DHT) levels appeared to parallel those of T on the three forms of therapy, with DHT:T ratios being highest for TU therapy. This was also true for the target organ metabolite 5 alpha-androstane-3 alpha,17 beta-diol. At the doses studied drug costs were similar for T implantation (every 5 months) and T ester injections (every 3 weeks), but were 7-8 times higher for TU (80 mg twice a day). We conclude that T implantation remains overall the most physiological form of androgen replacement therapy, is generally well accepted and attended by few side effects; TU may have a useful role in the initial phases of therapy.

Androgens in the feedback regulation of gonadotropin secretion in men: effects of administration of dihydrotestosterone to eugonadal and agonadal subjects and of spironolactone to eugonadal subjects

To study the role of androgens in the feedback regulation of gonadotropin secretion, we measured the effects of administration of dihydrotestosterone undecanoate (DHTU) and of spironolactone. Basal and LRH stimulated LH/FSH levels were determined in: Six eugonadal men, before and after six weeks' DHTU 120 mg/day. Six agonadal subjects after 12 weeks' DHTU 120 mg/day. The results of B were compared to those of Six agonadal subjects without sex steroid treatment. Six eugonadal subjects were studied before and after six weeks' administration of spironolactone. In the two groups of eugonadal subjects, administration of either dihydrotestosterone or spironolactone had no effect on basal and LRH-stimulated gonadotropin levels. A clear but modest suppression was observed in agonadal subjects. Possibly DHT exerts some suppressive effect on gonadotropin secretion in the absence of other testicular products (estradiol, testosterone, inhibin), known to play a role in the negative feedback regulation. From these data it seems unlikely that in the eugonadal male circulating DHT has an important role in the feedback regulation of gonadotropin secretion.

Basal and LHRH-stimulated gonadotropin levels and the circadian rhythm of testosterone and the effect of exogenous testosterone thereon

In seven eugonadal men, aged 20-26 years, a fall in plasma and saliva testosterone (T) levels between 8.00 and 16.00 h of the day was observed, but plasma oestradiol-17 beta levels did not show a significant variation. These findings substantiate the existence of a circadian rhythm in T levels. Concurrent with the decrease of T levels over the day, a small but significant rise in basal LH, but not in LHRH-stimulated LH levels were observed. Then the fall of plasma and saliva T levels over the day was prevented by the administration of 80 mg testosterone undecanoate (Andriol, Organon) by mouth at 8.00 h. A rise in plasma T and even more in saliva T levels was measured, which persisted till at least 16.00 h. At this hour basal LH, but not LHRH-stimulated LH levels appeared to be slightly, though significantly depressed. From our data we conclude that fluctuations of T levels of the magnitude of 25% around the baseline values, affect slightly basal LH levels, but not LHRH-stimulated LH levels.

Prolactin secretion in the human male is increased by endogenous oestrogens and decreased by exogenous/endogenous androgens

There is evidence that prolactin may be involved in testicular steroidogenesis, and we have therefore investigated whether there is feedback regulation of androgens/oestrogens on prolactin secretion in the human male. To assess this we have measured basal and TRH-stimulated prolactin levels in: Six eugonadal men before and after 2 weeks' administration of the aromatase inhibitor delta'-testolactone, which led to a fall in oestradiol levels with unchanged levels of testosterone. In these patients, prolactin levels decreased. Six eugonadal subjects before and after 6 weeks' administration of dihydrotestosterone undecanoate. In these subjects, prolactin levels decreased. Six agonadal subjects, tested after 12 weeks' treatment with dihydrotestosterone undecanoate and compared to: Six agonadal subjects who received no sex steroid treatment. Again, it was found that dihydrotestosterone treatment decreased prolactin levels in patients from Group C. Six eugonadal subjects were also studied before and after 6 weeks' administration of the androgen receptor antagonist, spironolactone, and this treatment increased Prl secretion. It is concluded that in the human male, endogenous oestrogens increase prolactin secretion whilst exogenous/endogenous androgens decrease prolactin secretion.

The behavioural effects of testosterone undecanoate in adult men with Klinefelter's syndrome: a controlled study

The behavioural effects of exogenous testosterone in men with marginally low circulating androgen levels were investigated. Four adult men with Klinefelter's syndrome, low normal testosterone levels and normal sexual activity and interest were given testosterone undecanoate (TU 160 mg daily by mouth; Organon International) and placebo using a double blind cross-over design. A modest increase in sexual interest was observed during TU administration compared to placebo, though there were no effects on self-reported mood or energy, or on erectile responsiveness in the laboratory. Increase in circulating hormone levels during TU administration was more marked for DHT than for testosterone. The possible implications of this are discussed.

The effect of puberty and short-term oral administration of testosterone undecanoate on GH tests and sex-steroid related plasma compounds in GH deficient patients

In twelve boys and two girls, with idiopathic (partial) growth hormone deficiency diagnosed at prepubertal age, we studied the effect of spontaneous puberty (six patients) as well as the effect of sex-steroid priming (eight patients). Six boys received testosterone undecanoate and two girls ethinyloestradiol for 5 days. Two pubertal patients showed a normal GH response, the patients primed with testosterone or oestrogen did not, despite a distinct effect on sex-steroid related plasma compounds. Reevaluation of GH status appears to be worthwhile in GH deficient patients presenting with short stature, growth deceleration at an early pubertal age and delayed sexual maturation. Sex-steroid priming is unlikely to alter the outcome of GH testing, whenever marked growth deceleration is evident at prepubertal age.

Testosterone metabolism by the rat gastrointestinal tract, in vitro and in vivo

We have shown previously that the capacity of the jejunal mucosa to oxidise testosterone to the weaker androgen, androstenedione, by the enzyme 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD), is considerable. The present study extends these earlier observations by measuring 17 beta-HSD activity in different regions of the gastrointestinal tract, by investigating the potential for testosterone metabolism by slices and everted sacs of rat jejunum, and estimating the contribution of intestinal testosterone metabolites to circulating levels of plasma androgens, by portal vein sampling in the rat, in vivo. 17 beta-HSD activity in homogenates of gastric and duodenal mucosa was significantly higher than that in jejunum, and was also present in ileum and colon. In addition to androstenedione, slices and everted sacs of rat jejunum produced various metabolites, one of which was probably dihydrotestosterone. It was not, however, a major metabolite in vivo. It is suggested that 5 alpha-reduction may be favoured in vitro by a lower oxidation-reduction potential resulting from tissue anoxia. The major portal vein metabolite was androstenedione, the same major metabolite produced by mucosal homogenates. We conclude that oxidation of testosterone is the major metabolic pathway in intestinal mucosa and the capacity of the gastrointestinal tract to reduce the potency of testosterone is considerable. Our findings suggest that the gut, rather than the liver, is responsible for the failure of oral testosterone to provide effective androgen replacement therapy. The qualitative difference in testosterone metabolism between in vitro and in vivo preparations emphasises the need for caution in the interpretation of similar in vitro experiments.

Clinical efficacy of testosterone undecanoate in male hypogonadism

Testosterone undecanoate (Restandol, Organon Laboratories Ltd) dissolved in oleic acid, was administered orally to seventy-six hypogonadal males for three consecutive 3-week periods and the subjective clinical response assessed by a standard interview. Plasma testosterone and testosterone undecanoate levels were determined by radioimmunoassay before the study and after 3, 6 and 9 weeks treatment. The treatment was effective in sixty of the sixty-six patients who completed the trial. Ten patients did not complete the trial; two for reasons unrelated to the drug and eight because of side effects, mainly gastro-intestinal. There was a significant rise in plasma testosterone levels during treatment and a positive correlation between plasma testosterone and testosterone undecanoate levels. Testosterone undecanoate is a potentially valuable drug for the oral treatment of male hypogonadism.

Androgen replacement with oral testosterone undecanoate in hypogonadal men: a double blind controlled study

The effects of androgen withdrawal and replacement were investigated in six hypergonadotrophic and six hypogonadotrophic men with hypogonadism. A double blind cross-over design was used comparing testosterone undecanoate (T.U., Organon International), 160 mg daily by mouth, with placebo. There was a significant effect of T.U. on all measures of sexual interest and behaviour. Sexual interest increased within the first week of T.U. administration, ejaculation usually returning within the second week. Behavioural responses were similar in the hyper- and hypogonadotrophic groups. The rise in plasma testosterone during T.U. administration was modest, not reaching the normal range in several cases. 5 alpha dihydrotestosterone rose more substantially. There was a significant fall in sex hormone binding globulin, a rise in oestradiol and no significant change in gonadotrophin concentrations during T.U. administration.

The use and misuse of androgens

Because testosterone is rapidly metabolized by the liver, it is necessary either to administer androgens by injection in the form of testosterone esters that are absorbed slowly into the circulation or to administer by mouth derivatives that are slowly metabolized by the liver. The later derivatives, however, have deleterious side effects that limit their usefulness. Long-acting parenteral androgen esters are the treatment of choice in the replacement therapy of male hypogonadism. Because these esters must be hydrolyzed to the free hormone prior to exerting their cellular actions the effectiveness of therapy can be monitored by following plasma testosterone levels. All known effects of the endogenous hormone can be duplicated except for the induction and maintenance of normal spermatogenesis. Androgens have been tried in a variety of clinical situations other than male hypogonadism in the hopes that the nonvirilizing actions would outweigh any detectable side effects. The only disorders in which a salutary effect has been documented are hereditary angioneurotic edema and some patients with anemia due to failure off the bone marrow.

Androgen substitution with testosterone containing nasal drops

Testosterone proprionate in form of eye drops will not be absorbed. A good absorption takes place following the administration of testosterone containing nasal drops in the form of an emulsion of pure testosterone. A quick, significant testosterone increase but of only short duration takes place. Unpleasant side effects were not observed. This treatment may be clinically applicable to male patients in the climacteric period.

Double-blind group comparative study of testosterone undecanoate and mesterolone in hypogonadal male patients

A double-blind, randomized, group comparative study was performed in hypogonadal male patients in order to compare the effects on sexual activity and mental state of testosterone undecanoate (TU) and mesterolone (M). The TU-treated group contained 12 patients, and the M-treated group contained 14 patients. The variables of sexual activity and of mental state were scored an evaluated statistically by means of the nonparametric randomization test for 2 independent groups. TU induced a marked improvement of the sexual activity and of the mental state. After 4 weeks of treatment the effects were significantly better than in the M-treated group: libido (p less than 0.001), erections (p less than 0.01), ejaculations (p less than 0.05) and mental state (p less than 0.001).

Clinical trial with testosterone undecanoate for male fertility control

The newly available orally effective testosterone undecanoate (TU) was investigated as a possible means for male fertility control. One of 7 normal volunteers exposed to 80 mg TU three times a day for 10-12 weeks became azoospermic, the remaining showed slightly suppressed or unaffected sperm counts. The insufficient suppression of spermatogenesis in 6 out of 7 subjects may be due to the fact that testosterone levels are only sufficiently high to suppress gonadotropins for some hours after ingestion of the drug.