Total Estrogen Excretion Research Articles

Occurrence and emission of phthalates, bisphenol A, and oestrogenic compounds in concentrated animal feeding operations in Southern China

Phthalates (PAEs), bisphenol A (BPA), and oestrogenic compounds have become major concerns due to their endocrine-disrupting effect. However, few studies related to the occurrence of PAEs, BPA, and oestrogen in food and compost from different growth age livestock have been conducted. In this study, faeces, urine and food samples were collected from a typical livestock (cow) and a special livestock (pigeon) from concentrated animal feeding operations (CAFOs). The daily total oestrogen excretion of a single cow ranged from 192 μg/day to 671 μg/day, which was significantly higher than that of a single pigeon (0–0.01 μg/day). Conjugated oestrogens represented 22.0–46.0% of the total oestrogens excreted from cow faeces and 80.7–91.8% of those from cow urine, indicating that the form of the excreted oestrogens depends on the livestock species and type of excrement. BPA was all detected in all livestock manure and food, and the concentration in pigeon was 9.2–40.2 ng/g and 23.1 ng/g respectively, while that in cattle was 50.5–72.0 ng/g and 41.1 ng/g respectively. The results indicated that the food is significant sources of BPA entering the process of cow and pigeon breeding. Diethyl phthalate (DEP) was detected at high frequency in pigeon faeces samples, suggesting that pigeons were highly exposed to these plasticisers. The total oestradiol equivalent quantity (EEQt) of livestock origin in aquatic environments was estimated to be 2.99 ng/L, which was higher than the baseline hazard value (1 ng/L) (Xu et al., 2018). The study provides data on the emissions and sources of PAEs, BPA, and oestrogenic compounds from different livestock in CAFOs and demonstrates that food is a significant source of BPA entering livestock.

Total Urinary Oestrogen Excretion of Normal Pregnant Malaysian Women in The Last Trimester of Pregnancy*

Total Urinary Oestrogen Excretion of Normal Pregnant Malaysian Women in The Last Trimester of Pregnancy*

Hormone Studies in Malignant Trophoblastic Disease

HCG, total oestrogen and pregnanediol excretion in 24 hours collections of urine were measured in 15 patients suffering from malignant trophoblaslic disease before treatment, during treatment and during subsequent follow-up. During the period of observation there were four recurrences of the disease in three patients and two patients became pregnant. The additional information provided by the oestrogen and particularly the pregnanediol estimations allowed a clear distinction to be made between recurrence and a new pregnancy.

Consecutive Urinary Gonadotropin and Ovarian Hormone Excretory Patterns during LH-RH Analog Treatment in Female Patients with Central Precocious Puberty

To study the initial stimulative and subsequent suppressive effects of Luteinizing hormone releasing hormone analog (LHRH-a) therapy on the hypothalamic-pituitary-ovarian axis, serial urinary excretion of gonadotropin and ovarian steroids were investigated in 23 female patients with central precocious puberty. Among them, seven were treated with intranasal administration of buserelin (G1), seven with daily subcutaneous injection of buserelin (G2) and nine with subcutaneous injection of super-long-acting LHRH-a every 28 days (G3). After the initial therapy in G1, the levels of urinary gonadotropin excretion increased greatly with a high level persisting for a longer period. Responding to these increases, the levels of urinary total estrogen excretion increased to an excessively high maximum level. After the initial injection in G3, the levels of urinary gonadotropin and total estrogen excretion were augmented at the same time for a shorter period with a lesser excretion of urinary total estrogen. Ovarian cysts developed after urinary total estrogen attained a maximum and tended to grow depending on the duration and degree of high urinary total estrogen excretion.The size of ovarian cysts was greater in G1 than in G3. During therapy in all groups, the mean urinary gonadotropins were significantly suppressed compared with pretreatment. The mean urinary total estrogen excretory level during treatment in G1 was not significantly suppressed compared with before treatment, but on the other hand, with significant suppression in G3. During therapy, urinary FSH excretion increased within 24 hours of every injection of super-long-acting LHRH-a with a slight rise in LH only in all patients in G3 studied. Studies in many more patients are required because the number of subjects was limited in this study.

Ovulation induction in premature ovarian failure: a placebo-controlled randomized trial combining pituitary suppression with gonadotropin stimulation

To determine the effect of pituitary suppression with a GnRH agonist (GnRH-a) on the success of ovulation induction with exogenous gonadotropins in patients with premature ovarian failure (POF). Placebo-controlled, randomized, double-blind study. The data were analyzed with a Fisher exact test. A tertiary care academic center for Reproductive Endocrinology and Fertility. Thirty patients with POF, 15 in each group. The study consisted of four phases: phase 1, no interventions; phase 2, a 4-week period in which the patients received either 1,000 micrograms intranasal buserelin acetate daily or placebo; phase 3, a 3-week period during which the patients additionally received hMG in weekly augmented doses, two, four, and six ampules daily in the first, second, and third weeks, respectively. Ovulation was induced whenever the follicular diameter reached 18 mm and/or total 24-hour estrogen excretion > 140 micrograms (500 nmol). Luteal support was 5,000 IU hCG every 72 hours; phase 4, no interventions. Follicular growth was seen in five patients of the agonist group and in four patients of the placebo group. Three of 15 patients in the agonist group ovulated versus none in the placebo group. The difference was not statistically significant. The fact that 3 of 15 cycles cotreated with a GnRH-a were ovulatory versus none in the placebo-treated group appeared not to be enough evidence to demonstrate that pituitary suppression with a GnRH-a improves the success of ovulation induction with exogenous gonadotropins in patients with POF.

Estrogen Metabolism and Excretion in Oriental and Caucasian Women

Caucasian and Oriental women have different incidence rates of breast cancer. Among the underlying risk factors for the development of breast cancer in the women of these two groups may be their different diets and patterns of estrogen metabolism and excretion. The absolute levels and relative ratios of 16 alpha-hydroxylated estrogens and 2-hydroxylated estrogens (catechol estrogens) in the body may have a role in the etiology of breast cancer, but studies so far have provided only conflicting results. Our goal was to study estrogen metabolism, in particular, the extent of 2-hydroxylation and 16 alpha-hydroxylation of estrogens in two groups of women, one Caucasian and one Oriental, with inherently different breast cancer risks. Dietary records were analyzed over 3-day periods in the mid-follicular phase, twice, at 6-month intervals for 13 premenopausal Oriental women, recent immigrant arrivals in Hawaii with presumed low risk of breast cancer, and for 12 premenopausal Finnish women with presumed higher risk. The urinary estrogen profile was measured by gas chromatography-mass spectrometry and plasma and fecal estrogens were assayed by chromatographic radioimmunoassays. Mean fat intake per 1000 kcal was 73% higher (P < .001) in the Finnish women, but the mean fiber intake and fecal weights were similar to those of the Oriental women. Compared with Oriental women, Finnish women had 46% higher plasma estradiol (P < .01) and 124% higher plasma estrone sulfate (P < .01); however, after adjustment for differences in age and body mass index, only the difference in estrone sulfate remained statistically significant (P < .05). Mean plasma levels of estrone and estradiol correlated with height after adjustment for body mass index (P < .05). Mean plasma levels of estrone and sex hormone-binding globulin were similar. The Finns had higher mean urinary estrone (193%), estradiol (166%), various catechol estrogens (130%-439%), and total estrogen excretion (123%) (all P < .001), but similar 16 alpha-hydroxylated estrogen excretion. As calculated, 16 alpha-hydroxylation of estrone was significantly increased (P < .01) in the Oriental women, but 2-hydroxylation, 4-hydroxylation, and 16 beta-hydroxylation of estrone were similar in both groups. The ratio of catechol estrogen to 16 alpha-hydroxylated estrogen was four to five times higher (P < .001) in the Finnish women. The Oriental women had two to three times higher fecal excretion of estrogens than the Finnish women (P < .01). Our results indicate that high catechol estrogen formation may be a greater risk factor for breast cancer than high 16 alpha-hydroxylation of estrogens. However, the main risk factor for the Finnish women, as opposed to the Oriental women, may be their higher estrogen levels that result from a higher fat diet, higher estrogen production related to their greater height, and lower fecal estrogen excretion.

Plasma and urinary oestrogens in breast cancer patients on treatment with 4-hydroxyandrostenedione

Plasma and urinary oestrogens were measured in nine breast cancer patients (eight postmenopausal women and one man) before and during treatment with the aromatase inhibitor 4-hydroxyandrostenedione. Urinary oestrogens were measured by using a highly specific GC-MS method. Plasma levels of oestrone, oestradiol and oestrone sulphate were suppressed by 66.6% (+/- 3.6%), 57.7% (+/- 5.1%) and 51.8% (+/- 6.4%) respectively (P < 0.005 for all). Twenty-four hour urinary excretion of total oestrogens, oestradiol, oestriol, 2-hydroxyoestrone, 16 alpha-hydroxyoestrone and the minor metabolites 16 beta- and 15 alpha-hydroxyoestrone were all suppressed by mean values ranging from 60% to 82%, (oestradiol: P < 0.025, otherwise P < 0.005). There were no significant changes in the ratios between the different plasma oestrogens. The finding of sustained plasma and urinary oestrogens at 20-40% compared to their control levels indirectly support a hypothesis of alternative oestrogen sources in postmenopausal breast cancer patients on treatment with 4-hydroxyandrostenedione.

Inhibition of ovulation with oral progestins — effectiveness in premenstrual syndrome

Forty-eight women with premenstrual problems were recruited for therapy with either medroxyprogesterone (MPA) or norethisterone (NET), both compared with placebo, in a double-blind cross-over study. Thirty-five (73%) completed the study. At an oral dose of 15 mg daily for 21 days each cycle, both MPA and NET suppressed ovulation, although reduction of urinary total oestrogen excretion was significantly greater with NET. Breakthrough bleeding occurred in 74% of the cycles treated with MPA but only in 22% of those with NET. Symptoms were monitored daily by visual analogue scales. Both progestins significantly reduced breast discomfort, compared with placebo. While MPA significantly improved individual psychological symptom scores by the second active treatment cycle and pooled psychological symptom scores in both active cycles, NET was no more effective than the placebo. Similar numbers from both groups withdrew because of adverse effects. Among the women treated with MPA, the response to active and placebo therapy was related to the pretreatment psychological symptom profile. The results suggest that the beneficial effect of therapy with MPA in women with premenstrual problems was a consequence of disruption of menstrual cyclicity rather than a result of ovulation suppression.

Urinary Oestrogen Excretion in Benign Prostatic Hyperplasia and Prostatic Cancer

Urinary oestrogen excretion was measured in 20 healthy middle-aged men (controls), in 30 patients with benign prostatic hyperplasia (BPH) and in 32 prostatic cancer (PC) patients. The mean oestradiol (E2) excretion was significantly lower in the PC patients than in the controls and BPH patients. No other significant differences were found in oestrone (E1), oestriol (E3) and total oestrogen (E1 + E2 + E3) excretion between the 3 groups. The decreased E2 excretion in the PC patients is in accordance with our previous finding concerning significantly lower E2 plasma levels in PC patients. It seems possible that elderly men with lower endogenous oestrogen levels are at higher risk of developing cancer. On the other hand, the age-dependent increased oestrogen levels may play an aetiological role in BPH.

Successful artificial insemination in the giant panda (Ailuropoda melanoleuca) at ueno zoo

AbstractSuccessful breeding of the giant panda (Ailuropoda melanoleuca) following artificial insemination was achieved at the Ueno Zoo in 2 consecutive years (1985 and 1986). The first cub, born in June 1985, unfortunately died 43 hours after birth from being crushed by the mother panda; the second cub, born in June 1986, has been growing in good health. Electroejaculation and artificial insemination procedures were performed after immobilization with diazepam (0.1 mg/kg) and ketamine HCL (4.0–5.0 mg/kg). Semen of the male panda was collected by electroejaculation using a rectal probe with a diameter of 2.0 cm and with eight rings as electrodes. Stimulation of the male was given with 3 V (30–40 mA) over a 5‐sec period with 5‐sec intervals. The female panda exhibited estrus between late February and early March in 1985 and also between mid‐january and early February 1986. Increased excretion of urinary total estrogen showed coincidentally at maximum behavioral estrus, and a gradual rise of pregnanediol level was followed by artificial insemination. The gestational length for the first pregnancy was 110 days and that of the second 121 days.

Post-tubal sterilization problems correlated with ovarian steroidogenesis

Mid-luteal phase total urinary oestrogen excretion was found to be significantly reduced in women who had previously undergone tubal sterilization at least two years before assay; pregnanediol levels at or below 2.0 mg/24 hrs were significantly more frequent for the study group. These findings indicate that reduced ovarian function is associated with that procedure. The major problems declared as having been experienced subsequent to tubal sterilization were classified into three categories; some women declared problems in more than one category: 1. (1) Abnormal uterine bleeding and/or menorrhagia, 2. (2) Physical problems, 3. (3) Psychological and/or psychiatric problems. Category 1 was associated with a significant fall in total oestrogen excretion, and category 2 with a significant fall in both total oestrogen and pregnanediol excretion. Analysis of category 3 will be published elsewhere. A negative correlation between total oestrogens and cholesterol was observed.

The return to ovulation following early abortion: a comparison between vacuum aspiration and prostaglandin

The return to ovulation following early abortion (less than or equal to 56 days amenorrhea) has been assessed after both vacuum aspiration under general anesthesia (N = 14) and menstrual induction with 16,16 dimethyltrans-delta 2PGE1 methyl ester in pessary form (N = 18). The urinary excretion of hCG, total estrogen and pregnanediol was similar in each group. There was an initial rapid decline in hCG excretion (t1/2 48 h), reaching 10% of the pre-treatment value after 6 days. Twenty-nine (91%) women showed a luteal phase rise in pregnanediol excretion, with ovulation occurring on day 29 (16-37) and 24 (16-32) in the vacuum aspiration and prostaglandin groups, respectively (median (range) NS). The wide range in the return of ovarian activity was related to the variation in decline of progesterone secretion (as reflected by excretion of pregnanediol) by the corpus luteum. Asynchrony between the ovarian and menstrual cycles resulting from a delay to ovulation presents a major constraint to the use of early pregnancy interruption as a routine method of fertility control.

Monitoring of pregnancy in diabetes mellitus

From 1970-1984 116 diabetic pregnant patients were monitored and delivered at the University Hospital of Freiburg, Department of Obstetrics and Gynaecology. The pregnant diabetics were managed and controlled by an interdisciplinary team of internists and obstetricians. For better control of the maternal metabolic status, the diabetic patients were admitted to the hospital three times during their pregnancy. Foetal monitoring was done by ultrasonography, hormone analyses and cardiotocography. In most cases foetal growth retardation and macrosomia were detected early via sonography. Decreased urinary excretion of total oestrogen was measured during late pregnancy in 13% of the diabetic patients. In cardiotocography a loss of foetal reactivity was observed in 11% of all non-stress tests (NST). In more than 50% of these cases, the total oestrogen excretion also decreased. In patients with normal oestrogen values, an abnormal NST was rarely observed. Abnormal oxytocin challenge tests (OCT) were recorded in 19% of the patients. Among these cases most of the patients with a non-reactive NST were found. In 85% of the patients with pathological changes in the OCT a Caesarean section had to be performed, and among these in all patients with a loss of foetal reactivity in the cardiotocogram. In correlation with the foetal outcome, loss of reactivity in the cardiotocogram has greater pathological relevance than deceleration with maintenance of reactivity. For an early recognition of imminent placental insufficiency, OCT proved to be the most sensitive parameter. The increased incidence of acute placental insufficiency in diabetics during delivery underlines the need for repeated stress tests during late pregnancy.

Sex differences in uric acid metabolism in adults: Evidence for a lack of influence of estradiol-17β (E 2) on the renal handling of urate

The serum urate concentration of adult women, which is lower than in men of a similar age, is thought to be related to a higher renal clearance of urate in women, possibly due to their higher plasma estrogen levels. Intersexual differences in the renal handling of uric acid was assessed in 9 normal adult women and 9 normal age-matched men. Women showed a significantly lower serum urate concentration as compared to men (3.5 ± 0.3 v 4.9 ± 0.7 mg/dL, P < 0.001), higher fractional excretion of urate (9.8 ± 1.0 v 7.3 ± 0.8%, P < 0.001), and significantly lower tubular urate postsecretory reabsorption (67.2 ± 1.6 v 76.6 ± 1.4% of secreted urate, P < 0.01). To test whether plasma E 2 has a uricosuric effect we administered estradiol valerate and estradiol benzoate to either oophorectomized or adult women. Plasma E 2 levels and urinary total estrogen excretion increased significantly in both groups but the treatment failed to significantly modify serum urate or the fractional excretion of uric acid. Furthermore, in 4 normal adult women, the tubular phases that modulate the renal excretion of urate were not significantly influenced by increased plasma E 2 levels. We conclude that in comparison to men of a similar age, the lower tubular urate postsecretory reabsorption of adult women is in accordance with the intersexual differences in uric acid metabolism. Plasma E 2 does not influence renal handling of uric acid or serum urate levels.

Effects of portal vein ligation on sex hormone metabolism in male rats: Relationship to lowered hepatic cytochrome P450 levels

Hepatic cytochrome P450 levels in male rats fall after portal vein ligation, a procedure that produces total hepatic bypass of portal blood. The present study was undertaken to examine whether changes in sex hormone metabolism could account for these lowered cytochrome P450 levels. Portal vein ligation resulted in testicular atrophy and low serum testosterone concentrations. Serum luteinizing hormone levels were also reduced, suggesting that testicular atrophy was secondary to suppression of the hypothalamic-pituitary-gonadal axis. Serum estrone and estradiol concentrations were significantly increased after portal vein ligation, while the magnitude and delayed onset of increases in urinary total estrogen excretion suggested that this was due largely to increased estrogen production. In male rats, both castration (at 12 wk) and exogenous estrogen administration resulted in changes in hepatic cytochrome P450 levels and ethylmorphine N-demethylase activity that were qualitatively similar to those seen after portal vein ligation. In female and castrated male rats, however, cytochrome P450 was not affected by portal vein ligation. Testosterone supplementation corrected the changes of cytochrome P450 levels in castrated male rats but did not have this effect in portal vein-ligated male rats. It is concluded that changes in sex hormone metabolism do occur after portal vein ligation and may contribute to alterations in cytochrome P450 and drug-metabolizing enzyme activity. Decreased levels of serum testosterone, however, do not alone account for the changes in hepatic drug metabolism in this model, and suppression of a hypothalamic-pituitary factor appears to be important.

Urinary estrogen profile determination in young finnish vegetarian and omnivorous women

For a long time it has been postulated that diet may influence estrogen metabolism and in this way affect breast cancer risk. In order to investigate possible effects of variations of dietary fiber intake on estrogen metabolism, the urinary estrogen profile (13 estrogens), including the catecholestrogens, was determined in one 72-h summer and one winter sample collected in the midfollicular phase of the menstrual cycle by 11 lactovegetarian and 12 omnivorous young Finnish women. Urinary estrogens were purified by ion-exchange chromatography and the quantitative determination was carried out by capillary gas chromatography-mass spectrometry. Detailed records of the subjects' diet during one 5-day period in summer and one in winter were obtained and dietary fiber intake calculated. The mean difference with regard to intake of total fiber in the two dietary groups was 3 g/day in the summer (not significant) and 5g/day in the winter ( P < 0.05), the mean (geometric) consumption being 23 and 19 g/day by the vegetarian and omnivorous women, respectively. Within the groups we found seasonal variation in fiber intake only for the omnivorous women. During winter, compared to summer, the omnivorous women consumed significantly less grain ( P < 0.001), vegetable ( P < 0.02) and total fiber ( P < 0.02). The excretion of 13 estrogens was remarkably constant in the omnivoric group but a significant seasonal variation of total and individual catecholestrogens and of estrone was observed in the vegetarians ( P < 0.05–0.005). The quantitatively most important estrogen was 2-hydroxyestrone, followed by estrone, estriol, 2-hydroxyestradiol, 4-hydroxyestrone and estradiol, the three latter being excreted in similar amounts. Between the dietary groups there were no significant differences in excretion of total or individual urinary estrogens in any season or between the mean values for both seasons. However, numerous significant ( P < 0.05–0.01) negative correlations between dietary intake of total or grain fiber/kg body weight and the excretion of individual estrogens were found. These correlations disappeared if the fiber intake was not related to body weight. We conclude that dietary fiber intake significantly affects estrogen metabolism by reducing estrogen excretion in urine and that grain fiber seems to be most important in that respect. One of the mechanisms involved is a partial interruption of the enterohepatic circulation of the estrogens, due to alterations of the intestinal metabolism and reabsorption of these steroids, caused by the fiber.

Excretion of total estrogens and estrone-3-glucuronide during treatment with human menopausal gonadotropins

HMG treatment is usually monitored by the evaluation of the cervical mucus, the determination of plasma 17β-estradiol, total urinary estrogens, ultrasonographic evaluation or a combination of these. We evaluated the daily validity of estrone-3-glucuronide excretion in urine as an indicator of follicular growth and maturation in 28 infertile women who were treated with HMG (Pergonal 500). Total urinary estrogens and estrone-3-glucuronide were measured in 24 h urine collections, and 11 of the women collected the early-morning urine separately. This allowed comparison of the concentrations and excretion of total estrogens and estrone-3-glucuronide of the 24 h urine with that found in the urine collected overnight. This comparison was made on 83 urine samples. The correlation between either the total excretion per 24 h or the concentration per liter in the 24 h urine collection of the two systems of determination was good in all determinations. Also in the urine collected on the day prior to HCG administration, total estrogens measurement was in good correlation with the estrone-3-glucuronide. However, there was statistically a significant difference in the concentrations of total estrogens and estrone-3-glucuronide between the women who ovulated and those who did not. Estrone-3-glucuronide, when calculated as a percentage of the total estrogens, was 60.86% in the women who ovulated and 33.15% in those who did not. These results demonstrate that although estrone-3-glucuronide reflects ovarian function in women treated with HMG, it may serve as a better predictor to ovulation.

SEX DIFFERENCES IN URIC ACID METABOLISM INADULTS: EVIDENCE FOR A LACK OF INFLUENCE OF ESTRADIOL-17β (E2): 165

The lower serum urate concentration of age-fertile women compared to men is thought to be related to a higher renal clearance of urate possibly detrmined by plasma estrogen levels. We assessed renal handling of uric acid in 9 normal age-fertile women compared to 9 age-matched men. Women showed significantly lower serum urate concentrations than men (3.5 ± 0.3 vs. 4.9 ± 0.7 mg/dl, P < 0.001), higher fractional excretion of urate (9.8 ± 1.0 vs. 7.3 ± 0.8 percent, P < 0.001) and lower tubular urate postsecretory reabsorption (P <0.01). To test the hypothetical uricosuric effect of plasma E2 we administered estradiol valerate and estradiol benzoate to oophorectomized and age-fertile women, respectively. Plasma E2 levels and urinary total estrogen excretion increased significantly but failed to substantially modify serum urate or the fractional excretion of uric acid. Furthermore, in 4 normal age-fertile women tubular urate transport was not influenced by plasma E2 levels. The lower tubular urate postsecretory reabsorption of age-fertile women compared to men is in accordance with their lower serum urate concentration and higher fractinal excretion of uric acid. Plasma E2 does not influence renal handling of uric acid.

Urinary estrogens during pregnancy of the ruffed lemur (Lemur variegatus).

Pregnancy in the ruffed lemur (Lemur variegatus) was monitored by analyses of urinary estrogens. Urine samples were collected weekly throughout pregnancy (gestation: 100 +/- 1.6 days) from ten females analyzed for total immunoreactive estrogen (Et) and indexed by creatinine (Cr). Maternal urinary total estrogen excretion remained low until the last half of gestation at which time excretion increased steadily, reaching values 1000 times greater than those observed at estrus. Chromatographic separation after enzyme hydrolysis of lemur urine indicates that estrone is the major estrogenic component of pregnancy in the ruffed lemur, with the remaining components consisting of equal amounts of estradiol-17 alpha and -17 beta.

Several examinations on the reproductive status of lowland gorillas (Gorilla g. gorilla) at Hannover Zoo

AbstractThere as been no reproduction within the Hannover Zoo's gorilla group, although several adult females and a silverback male have been living together for a prolonged period. Therefore, the sexual cycle of three adult females was examined by means of total urinary estrogen excretion, measurement of the urogenital cleft length, ovulation detection with the help of the Subhuman‐Primate‐Pregnancy Test (SPPT), measurement of basal body temperature, semiquantitative blood tests to detect menstruation, and observation of sexual behavior. Fertility status of the silverback male was examined by means of behavioral observation, rectal probe ejaculation (RPE), and testicular biopsy. Sexual cyclicity was demonstrable in two females, whereas the third had an irregular occurrence of estrogen peaks and her menstruation and sexual behavior did not show normal cyclicity. The male's infertility was characterized by absence of any sexual behavior, azoospermia in repeated RPE, unsuccessful treatment with clomiphene, and atrophy of seminiferous tubules in the extirpated tissue.Several factors, such as vitamin E deficiency, humoral dysregulation, testicular hypoxy, and spermatogenic arrest, caused through stress due to inadequate shelter systems, are discussed hypothetically in regard to their possible etiological relevance with respect to infertility in this species.In many cases infertility in the gorilla male is presumably based on a polyfactoral etiology. Analysis of urinary hormone levels in parallel with behavioral studies is still to be tested as a practical method of gaining information on the puberty development of adolescent males and on the fertility status of adult males under zoo conditions.