Changes In Testicular Size Research Articles

Outcomes of Early vs. Late Surgical Intervention in Children With Undescended Testis.

Background Undescended testis (UDT) is one of the most common urogenital abnormalities. International guidelines recommend performing orchidopexy no later than 18 months to decrease the risk of complications associated with UDT such as infertility and testicular malignancy.The aim of the study is to evaluate the outcomes of early versus late surgical intervention of UDT and to assess if the optimal age of orchidopexy is met. Methods This is a retrospectivecross-sectional study that included 258 pediatric patients' testes with no prior UDT intervention from January 2016 to December 2020. A chart review was used to collect the patients' data. Children included were categorized into two groups based on their age at the time of surgery (group A ≤ 18 months and group B > 18 months). Statistical differences were explored using Pearson's chi-squared test or Fisher's exact test for categorical variables or a Wilcoxon rank sum test for numerical variables. A p-value of <0.05 indicated statistical significance. Results The median age at the presentation among the overall cohort was 14 months. The median age at the presentation for group A was six months and group B was 35 months.Group A included 109 children and group B included 149 children. At the time of the surgery, the median age of patients was 23 months. The median age at orchidopexy for group A was 12 months and the median age for group B was 38 months. The time between diagnosis and surgery was significantly shorter among older children with a median duration of one month versus a median of five months among patients in the ≤18 months group (p = 0.003). The follow-up interval was at three and 12 months. The change in testicular size before and after surgeries was statistically significant, as most small testicles before surgeries had become normal in size after surgeries among the overall cohort (76.6%), patients aged ≤18 months (72.4%), and those aged >18 months (79.2%) (p< 0.001). Conclusion Most of the patients included in this study did not undergo orchidopexy at the optimal age recommended by the international guidelines. However, there was a statistically significant improvement in testicular size following orchidopexy in children with small UDT regardless of age at the time of surgery.

FRI438 A Unique Case Of Secondary Hypogonadism And The Covid Booster Vaccine

Abstract Disclosure: O.Z. Syed: None. M. Shakir: None. K. Sajid: None. A. Sood: None. N. Bansal: None. 38-year-old male with no past medical or surgical history presented for an evaluation of his low testosterone. The patient transports patients in the hospital, he denies any medication use, including steroids, opioids, and antibiotics. He has a biological 8-year-old son and denied any history of viral infection recently and denied any history of testicular trauma, mumps, or radiation therapy. He started having fatigue, chronic mild headache, and generalized weakness after receiving his third dose of covid vaccine in January, however, he denied any diplopia, galactorrhea, hirsutism, or sexual dysfunction. He did not report any side effects with the previous 2 covid vaccines. After a couple of months of persistent symptoms accompanied by 40 pounds of weight loss( half of which he regained in a few months without intervention), he went to his PCP for evaluation. On physical examination, there were no abnormalities seen and as per the patient, there was no change in testicular size either. The patient was found to have mildly elevated prolactin of 17.8 with low free and total testosterone of 134 accompanied by FSH of less than 1.0 and LH of 1.4. The remaining labs include but are not limited to CBC, CMP, TSH, Vitamin D, CK, Sex hormone-binding globulin, and cortisol. The autoimmune panel, Hepatitis, HIV, and tick panels were negative. While he was being worked up he tested himself multiple times for covid and was negative. The patient had an MRI done which did not show any mass or lesions. Furthermore, he also had a Chest x-ray and CT of his abdomen/pelvis along with an Ultrasound of the abdomen, which did not show any concerning findings. The patient was started on testosterone gel at the endocrinology clinic with regular follow-ups to assess for response and side effects.As per the currently available literature, there have been multiple associations made between Covid 19 infection and hypogonadism. There have been reports of low testosterone following covid 19 infections and conversely there have been worse outcomes of covid 19 related to men with lower levels of testosterone. This could possibly be due to ACE 2 expression on testicular cells or due to secondary inflammation and oxidative stress inhbitiing steroidogenesis. However no literature was found linking the covid 19 vaccine to secondary hypogonadim other than a case of pituitary apoplexy. These findings in light of our case warrant further research into possible association between the covid vaccine and hypogonadism. In patients presenting with generalized weakness and similar vague symptoms, we need to consider a history of covid vaccination as it could potentially be a cause of secondary hypogonadism. Furthermore, more detailed and larger-scale studies need to be done concerning the covid booster vaccines and hypogonadism. Presentation: Friday, June 16, 2023

Characteristics of testicular atrophy during testosterone replacement therapy (TRT)

ABSTRACT Objectives Testosterone replacement therapy (TRT) is a common treatment for late-onset hypogonadism. In addition to adverse events such as polycythemia, it is reported that TRT may cause testicular atrophy due to decreased gonadotropin; however, there are no reported studies that have actually observed the degree of atrophy. We investigated changes in testicular size in patients undergoing TRT and examined the characteristics of testicular atrophy. Subjects and Methods Testicular size was measured before treatment and at 3 months, 6 months, and every 6 months after treatment up to 24 months in 121 patients undergoing TRT for more than 3 months. The size of each testicle was measured using a punched-out elliptical ring orchidometer, and the average testicular volume was calculated. Patients showing testicular atrophy at 3 months after the start of TRT were classified as the atrophy group, and cases with no change were classified as the unchanged group. Results The age of the subjects ranged from 38 to 81 (mean 53.7 years). Overall, testicular volume decreased over time, from a mean of 16.5 ml before treatment to 13.7 ml at 24 months, with atrophy becoming significant from 6 months. In the atrophy group (60 cases), the atrophic tendency persisted after 6 months, whereas in the unchanged group, no atrophic tendency was seen after 24 months. The background factors of the two groups were compared. Among age, baseline testicular volume, testosterone, and method of TRT administration (injection or ointment), the items that showed significant differences between the two groups were baseline testicular volume and method of administration. Testicular atrophy was more likely to occur in patients with larger baseline testicular size or those treated with injectable formulations. Conclusion For patients with large testicular volume or anxiety about testicular atrophy, it may be better to recommend TRT in ointment form rather than injectable formulations. Disclosure Work supported by industry: no.

Magnified subinguinal varicocelectomy versus conservative methods in treatment of adolescent varicocele

Background Elimination of varicocele in adolescent with lower complication rates is the best treatment modality. Therefore, the ideal technique should aim to ligate all internal and external spermatic veins with preservation of spermatic arteries and lymphatics. Aim We compared the outcome of magnified subinguinal varicocelectomy versus conservative methods in the treatment of adolescent varicocele. Patients and methods A total of 40 adolescent males (aged between 15 and 19 years) with refluxing varicocele and affected semen parameters and testicular volume were included. Overall, 20 patients were treated by magnified subinguinal varicocelectomy and 20 patients treated by conservative methods. All patients were reevaluated and followed for 6 months by several semen parameters and changes in testicular size by Doppler ultrasound. Results A significant improvement was seen in postmagnified subinguinal varicocelectomy group regarding sperm volume, sperm motility, sperm count, progressive movement, vitality, abnormal morphology, testicular volume, and varicocele grade, but in conservative method group, patients showed significant improvement regarding percent of rapid sperm, progressive movement and vitality, and a slight increase in testicular volume. After 6 months, there was a significant difference between both groups regarding sperm volume, progressive movement, vitality, testicular volume, and varicocele grade, so magnified subinguinal varicocelectomy is superior to conservative methods in the management of adolescents with symptomatic varicocele.

Global Secular Trend of Gonadal Size in Men: Review and Analysis of Publications

Introduction. Notwithstanding the general increase in world population, there is a steady decline in birth rate. Studies have shown a tendency towards worsening of qualitative and quantitative indices of the ejaculate. From the foregoing we may also presume a decline in size of male gonads. Nevertheless, information about the tendency of change in testicular size in the population is currently unavailable.Purpose of the study. Assessment of global secular trend as regards changes in the size of testes in men.Materials and methods. A search was conducted on published scientific research in the English language and Russian language in Pubmed and eLibrary. Additional searches in citations of identifiable investigations. A selection of data from publications with metric characteristics of gonads in relatively healthy men aged 18‒60 years. The mean of values obtained were determined and homogenized with the aid of formulae for volume calculations. Statistical analysis of the data was carried out with the aid of the program STATISTICA for Windows v.10.Results. The search yielded 126 identified publications, published between 1902 and 2018. Analysis of the various works led to a selection of 33, which contained information that satisfied the inclusion criteria. Analysis of the obtained data did not reveal any trends in change of testicular size over the past century. Mean arithmetic weighted value was 17,43±5,64; 95% CI (17,32; 17,54).Conclusion. In the light of global trends towards a reduction in fertility, it is necessary to conduct a wide range of varied investigations in order to understand the nature of this process. Standardization of methods of assessment results obtained will help in reducing errors whilst assisting in the analysis of existing tendencies.

Changes in testicular size, echotexture, and arterial blood flow associated with the attainment of puberty in Dorper rams raised in a subtropical climate.

There is a paucity of information on the relationships of testicular morphology, echotextural attributes, and blood flow dynamics with pubertal development of rams raised in a subtropical climate. Forty-five Dorper rams (24 rams aged 8-11months and 21 rams aged 12-24months) were examined using a portable ultrasound scanner connected to a 7.5-MHz transducer. Computer-assisted analyses of testicular ultrasonograms utilized commercially available Image ProPlus® analytical software. Spectral Doppler scans of testicular arteries were performed immediately after scrotal (B-mode) ultrasonography to determine peak systolic velocity (PSV), end-diastolic velocity (EDV), resistive index (RI=[PSV-EDV]/PSV), and pulsatility index (PI=[SPV-EDV]/mean velocity) of the blood vessels. The length of the testes (9.7±0.3 compared with 9.0±0.2cm) and scrotal circumference (33.3±0.5 compared with 31.8±0.4cm) were greater (p<0.05) but testicular depth (4.5±0.1 compared with 4.9±0.08 cm) was less (p<0.05) in sexually mature compared with peripubertal rams. [Corrections added on 9 Jan 2019 after initial online publication: The testicular size values in the sentence were corrected.] There were no differences (p>0.05) between the two age groups of Dorper rams in blood flow indices of testicular arteries. Mean numerical pixel values (100.5±4.1 compared with 89.2±4.8) and pixel heterogeneity (25.6±0.6 compared with 23.6±0.5) of testicular parenchyma were greater (p<0.05) in peripubertal than in postpubertal rams. Semen volume was negatively correlated with PI of testicular arteries (r=-0.57, p=0.04). In summary, the attainment of sexual maturity in the rams of the present study was associated with significant changes in testicular length and depth, scrotal circumference, and parenchymal echogenicity/hetrogeneity but not in testicular volume and blood perfusion rates. Testicular artery PI can be used to predict the volume of ejaculate in rams.

Reproductive parameters of donkey jacks undergoing puberty

In male donkeys, puberty and the related events have been poorly characterized. The aim of this study was to evaluate the age at which male donkeys reach puberty, and characterize age associated changes in testicular size, testicular blood flow, serum testosterone concentration and semen quality. Every two months, starting at 6 months and finishing at 24 months of age, five male donkeys born in May to July were subjected to B-mode ultrasound examination to assess testicular size and scrotum content and blood serum sampling for testosterone concentration. From the age of 8 months, pulsed Doppler was employed to evaluate blood flow in the testicular artery. Testosterone serum concentration was evaluated via RIA. From the age of 12 months, monthly semen collections were attempted and semen was evaluated for sperm number, motility and morphology. Onset of puberty was defined as the first ejaculate containing ≥50 × 106 spermatozoa with ≥10% total motility. One of the donkeys was excluded from the statistical analyses due to a hydrocele presented during the study. Testes width was affected by age (P < 0.0001) and after an initial plateau increased linearly from 10 months of age. Pulsatility and resistivity indexes were also affected by age (P < 0.01), being significantly higher at 14 months than at 24 months. Testosterone serum concentration was affected by age (P < 0.0001) and was significantly lower at 6 months (0.1 ng/ml) compared to 22–24 months (≥0.8 ng/ml). Spermatozoa appeared in the ejaculate at a mean age of 18.7 months and puberty was attained between 19 and 20 months of age (mean: 19.5 months), between January and February. In conclusion, late spring born Amiata donkey colts reached puberty at 19–20 months of age. Puberty was accompanied by changes in testicular size, testicular blood flow and serum testosterone concentration.

Shear Wave Sonoelastography Findings of Testicles in Chronic Kidney Disease Patients Who Undergo Hemodialysis.

Chronic kidney disease (CKD) is known to cause significant deterioration in the function of the testicles and sexual dysfunction in male patients who undergo hemodialysis. The aim of this study was to show the changes in the testicles that occur as a result of hypogonadism secondary to CKD and to analyze the elasticity of the parenchyma by shear wave sonoelastography. In our study we included 28 male patients who undergo dialysis three times per week and 25 healthy volunteers. Firstly, B-mode ultrasonographic evaluation was performed in both testicles for structural analysis and to detect the presence of focal lesions. Afterward, the stiffness of the parenchyma was measured in kilopascals by shear wave sonoelastography. The CKD group had lower right, left, and mean testicular volumes (p<0.001). The CKD group also displayed greater right, left, and mean testicular parenchymal stiffness (p<0.001). CKD patients who undergo hemodialysis demonstrated significant changes in testicular size and stiffness in comparison to healthy volunteers.

Can Hypertrophy of the Contralateral Testis Predict the Absence of a Viable Testis in Infancy with Cryptorchidism: A Prospective Analysis.

This prospective study aimed to evaluate whether Contralateral compensatory testicular hypertrophy (CTH) is valid as a predictive tool for a non-viable testis in children aged between 6 and 18 months, and whether CTH is affected by mini-puberty. Seventy-two testes from 60 boys aged between 6 and 18 months were categorized into three groups: 24 testes contralateral to surgically removed non-viable testes (NVTs), 24 testes contralateral to surgically corrected undescended testes (UDTs), and 24 testes from a normal controls. Contralateral testicular length and volume were measured with ultrasonography and compared among the groups. Group 1 (NVT) had a significantly longer length and larger volume than group 2 (UDT). The length and volume of each group among three developmental periods (6–10, 10–14, and 14–18 months) were also analyzed. In the controls, the length was significantly larger at 6–10 months than at 10–14 months in accordance with previously reported changes in testicular size due to the effect of “mini-puberty.” The volume of controls showed a similar pattern, though without statistical significance. However, this pattern was not observed in the NVT and UDT groups. A receiver operating curve revealed that a testicular length of 16.1 mm or a volume of 0.59 ml had the highest sensitivity and specificity for predicting NVTs. The CTH was also found to be valid as a predictive tool for a NVT in children of ages 6 to 18 months, as the effect of mini-puberty appeared to be absent in the NVT and UDT groups. However, the cut-off values were less than those of previous reports. The proper cut-off level according to the age and measurement method should be applied in this developmental period.

Comparative investigation of two surgical techniques of orchiopexy in the post-operative recurrence rate and testicular size in children in clinical trial study

Background:Cryptorchidism is a common problem which is prevalent in 3% of male infants. This study aimed to determine the effect of both trans fixation and Dartos pouch fixation methods on the postoperative recurrence rate and testicular changes.Materials and Methods:In a clinical trial study, 70 children were randomly divided into two groups. In the first group, the correction of cryptorchidism was done by Dartos pouch without suture and in the second group; testis was sutured using common trans fixation. The size of testicles was measured before and 6 months after surgery, children were followed on postoperative complications, trauma to testicles and recurrence of disease in both groups. Data were analyzed using SPSS soft ware.Results:The mean size of testicles was 87.16 ± 20.6 mm2 in the group with fixed testicle and 182.4 ± 37.9 mm2 in the group with not-fixed testicle before operation and the difference between the two groups was significant (P = 0.013). After surgery, the mean size of testicles was 90.8 ± 19.9 mm2 in the group with fixed testicle and 183.7 ± 41.2 mm2 in the group with not-fixed testicle and the difference between them was significant (P = 0.026). The average of changes in testicular size was 3.62 ± 1.93 and 1.25 ± 5.35 mm2 in both fixed and not-fixed groups, respectively and changes in testicular size had no significant difference between the two groups. (P = 0.68).Conclusions:Type of fixation had no effect on the size of testes or relevance to the level of retraction. The above management protocol did very well in our hands, and we recommend it for application in the management of undescended testis.

Adolescent varicocele: limited indications for treatment during puberty and adolescence.

A varicocele is defined as an abnormal dilatation of the pampiniform plexus of veins of the testis. The vast majority of children and adolescents with varicoceles have no subjective symptoms. The complete work-up of patient diagnosed with a varicocele involves a physical exam in supine and prone position with and without Valsalva, and the use of ultrasound to measure testicular volume and blood flow. Because of growth issues occurring during puberty and adolescence, serial follow-ups may be done to determine any detrimental change in testicular size and symptomatology. The main difference of an adolescent varicocele is the fact that semen parameters are unavailable and do not count for treatment strategy. In this review, the focus is made on a recent study that has evaluated the ultimate endpoint: paternity. It appears that screening and treatment of a varicocele in the adolescent period does not influence the ultimate chance of paternity.

Testicular size development and reproductive hormones in boys and adult males with Noonan syndrome: a longitudinal study

To characterise changes in testicular size and reproductive hormones and to investigate the aetiology of delayed puberty and impaired fertility in males with Noonan syndrome (NS). In this study, 12 males with NS were longitudinally followed from pre/early puberty until adulthood. Of the 12 males, ten had no medical history other than NS and were divided into two groups, undescended testes (UT), and descended testes (DT) and compared with a reference population. Hormone concentrations in serum were determined by immunoassays and testicular volume was measured using an orchidometer. Before puberty, reproductive hormone levels were within the expected range in almost all cases. In some cases, LH, FSH and testosterone and oestradiol (E(2)) concentrations started to increase during puberty and inhibin B and anti-Müllerian hormone (AMH) declined to subnormal levels. Most of the boys studied had small testes that, in the majority of cases, progressed to normal size in adulthood. No difference in reproductive hormones was observed between the UT and DT groups either during puberty or at adulthood. However, as adults, males with NS had higher LH (5.7 vs 4.0 U/l, P<0.01), FSH (7.1 vs 2.5 U/l, P<0.001), testosterone (18.7 vs 15.6 nmol/l, P<0.01) and E(2) (66 vs 46 pmol/l, P<0.001) levels and lower AMH (33 vs 65 pmol/l, P<0.01) and inhibin B (median 108 vs 187 pg/ml, P<0.01) levels than the reference population. In NS males, both Sertoli and Leydig cell dysfunction is common with reproductive hormone levels deteriorating progressively to adulthood.

Changes in Testicular Development, Ultrasonographic and Histological Appearance of the Testis in Buck Kids Immunized Against LHRH Using Recombinant LHRH Fusion Protein

This study was designed to evaluate the effectiveness of recombinant Ovalbumin-LHRL (OL) immunization on changes in testicular size, histological appearance and testosterone production in buck kids. Thirty native buck kids at 18 weeks of age were divided into three groups, control (n = 10), immunization (n = 10) and castration (n = 10) groups. Immunized animals received OL protein generated by recombinant DNA technology. Ultrasonographic and histological examinations of the testes were performed. Animals were slaughtered at 44 weeks of age. Semen and epididymides were evaluated for the presence of sperm cells. Immunized animals generated anti-LHRH antibodies. Testosterone production, testicular and accessory glands development and sperm production were suppressed in the immunized animals (p < 0.01). Semineferous tubule diameters decreased (p < 0.01), basal membrane of the tubule was thickened and hyalinized in immunized kids. Immunization affected ultrasonographic appearance of the testes drastically. While testes of control animals gained their normal ultrasonographic appearance as the age increased, immunized animals had uniform hypoechogenic testicular structure as observed at 18 weeks of age until slaughter. Simultaneous histological and ultrasonographic evaluations indicated that the changes in testicular histology could partly be monitored via ultrasonographic imaging; nevertheless, it is difficult to claim that ultrasonographic image reflects the exact changes in such instances. In conclusion, these results indicate that recombinant OL fusion protein is effective in immunocastration in buck kids and has a potential to be used as an alternative to physical castration. Further researches should be conducted to help assessing reproductive status of testes from ultrasound images.

Ambient temperature effects on photo induced gonadal cycles and hormonal secretion patterns in Great Tits from three different breeding latitudes

The present study determines how populations of Great Tits ( Parus major) breeding in southern, mid and northern European latitudes have adjusted their reproductive endocrinology to differences in the ambient temperature during the gonadal cycle. A study based on long-term breeding data, using the Colwell predictability model, showed that the start of the breeding season has a high predictability (≈ 0.8–0.9) at all latitudes, and that the environmental information factor ( I e) progressively decreased from mid Italy ( I e > 4) to northern Finland ( I e < 1). The results indicate that integration of supplementary information, such as ambient temperature, with photoperiodic initial predictive information (day length), becomes progressively more important in maintaining the predictability of the breeding season with decreasing latitude. This hypothesis was verified by exposing photosensitive Great Tits from northern Norway, southern Sweden and northern Italy to sub-maximal photo-stimulatory day lengths (13L:11D) under two different ambient temperature regimes (+ 4 °C and + 20 °C). Changes in testicular size, plasma levels of LH and testosterone were measured. The main results were: (1) Initial testicular growth rate, as well as LH secretion, was affected by temperature in the Italian, but not in birds from the two Scandinavian populations. (2) Maximum testicular size, maximum LH and testosterone levels were maintained for a progressively shorter period of time with increasing latitude, regardless of whether the birds were kept on a low or a high ambient temperature. (3) In birds from all latitudes, the development of photorefractoriness, as indicated by testicular regression and a decrease in plasma levels of LH and testosterone, started much earlier (with the exception for LH Great Tits from northern Scandinavia) when kept on + 20 °C than when kept on + 4 °C. The prolonging effects of a low temperature was more pronounced in Mediterranean birds, than in birds from Scandinavia, and more pronounced in Great Tits from southern Scandinavia than in Great Tits from northern Scandinavia. Ecological implications of the results are discussed, as well as possible impact of global warming on the breeding success of European Great Tits from different breeding latitudes.

Annual Changes in Testicular Size and Serum and Fecal Testosterone Concentrations in Male Bharals, Pseudois nayaur

The serum and fecal testosterone (T) concentrations and testicular sizes of two male bharals (Pseudois nayaur) were determined for approximately one year. The profiles of the fecal T concentrations showed a similar tendency as the profiles of serum T concentrations, and there was a significant correlation between serum and fecal T concentrations (r=0.72). T concentrations rose drastically in October and decreased gradually until January. The maximum testicular size was observed between November and January. Semen collected between December and January was excellent in quality and comparable to domestic sheep and goats. The active periods of the testes were synchronized with the early breeding season of females.

PRIMARY TESTICULAR BURKITT LYMPHOMA IN A CHILD

A 13-year-old boy was referred to the authors' hospital following a right inguinal orchiectomy for a right scrotal mass. Histopathological examination revealed Burkitt lymphoma. The left testis was found to be small with heterogeneous parenchyma by scrotal ultrasound (US) and other systemic investigations were negative for lymphoma involvement. Ultrasound-guided fine-needle aspiration biopsy showed no evidence of involvement in the left testis. Considering stage I Burkitt lymphoma, chemotherapy was started. Following the first course, US findings changed: the volume of the left testis decreased and the parenchyma became homogeneous. The left testis was considered to be involved by lymphoma at initial diagnosis and chemotherapy was intensified. At the end of 5 months of chemotherapy the left testis was again heterogeneous in US. A wedge-biopsy was negative for lymphoma. The patient is under regular follow-up and is in complete remission 19 months after the end of chemotherapy. Primary testicular lymphoma is quite rare in children and experience is limited. Changes in testicular size and parenchyma by US should not necessarily indicate involvement by lymphoma in pubertal boys.

Evidence that the photoperiod controls the annual changes in testosterone secretion, testicular and body weight in subtropical male goats.

The aim of this study was to determine whether the reproductive seasonality of local male goats from subtropical Mexico (26 degrees N) is controlled by photoperiod. The control group (n = 7) remained in an open shed under natural daylight. The two experimental groups (n = 6 each) were placed in light-proof buildings and exposed for 2 years (yr) to alternations of 3 months (mo) of long days and 3 mo of short days. One group was first exposed to long days and the other one to short days. Body and testicular weights were determined every 2 wk. Blood samples were obtained weekly to determine testosterone plasma concentrations. In the control group, the body weight exhibited variations (P < 0.0001) and it increased during the non-breeding season. In both treated groups, long days stimulated weight gain and short days inhibited it (P < 0.0001). In the control group, testicular weight displayed variations (P < 0.0001), and high values were registered in June. In the treated groups, a testicular weight reduction occurred 6-9 mo after the onset of the study. Afterwards, the changes in testicular size varied according to daylength (P < 0.01). The pattern of plasma testosterone concentration in the control group varied over the study (P < 0.0001) and the levels were higher from May-June to November. In both treated groups, the changes in testosterone secretion occurred according to photoperiod changes (P < 0.0001). Short days enhanced testosterone secretion one photoperiodic cycle after the onset of the study and long days inhibited it. Local male goats from subtropical Mexico are sensitive to photoperiodic changes and this environmental cue may control the timing of the breeding season in natural conditions.

Annual changes in testicular size, plasma testosterone concentration, home range and active time in wild male marten, Martes melampus melampus

Annual changes in testicular size, plasma testosterone concentration, home range and active time in wild male marten, Martes melampus melampus

Seasonal changes in testicular size and serum LH, prolactin and testosterone concentrations in male polar bears (Ursus maritimus).

Little is known about the reproductive endocrinology of the male polar bear, Ursus maritimus, except that serum testosterone concentrations are high in April and May during the mating season and are low from August to November during the non-mating season. The objective of this study was to describe the relationship between seasonal changes in testicular size and serum concentrations of testosterone, LH and prolactin. Blood samples and testicular measurements were obtained from free-ranging male polar bears in Canada in April (n = 5) and May (n = 15) near Resolute Bay, Northwest Territories and near Churchill, Manitoba in July (n = 15) and October (n = 22). Testis size was greater in May (39.4 +/- 3.5 cm(2)) than in October (27.3 +/- 2.0 cm(2)) (P = 0.002). Serum testosterone concentrations were approximately three-fold higher in April (5.8 +/- 0.8 ng ml(-1)) than in May (1.7 +/- 0.5 ng ml(-1)), July (0.6 +/- 0.2 ng ml(-1)) and October (1.1 +/- 0.2 ng ml(-1)). Similarly, serum LH concentrations were high in April (0.14 +/- 0.04 ng ml(-1)) and low in May (0.09 +/- 0.01 ng ml(-1)), July (0.10 +/- 0.02 ng ml(-1)) and October (0.08 +/- 0.00 ng ml(-1)). Serum prolactin concentrations were high in April (1.9 +/- 0.3 ng ml(-1)), highest in May (2.5 +/- 0.2 ng ml(-1)), lower in July (1.3 +/- 0.1 ng ml(-1)) and lowest in October (0.8 +/- 0.07 ng ml(-1)). The present study demonstrates a positive relationship between testicular size and serum concentrations of LH, prolactin and testosterone in the male polar bear and confirms the previously reported seasonal changes in serum testosterone concentrations. Data from the present study provide important baseline and comparative endocrine information that can be used to aid captive breeding programmes in zoos and to further ecological-behavioural studies of polar bears.

Seasonal changes in testicular size and serum LH, prolactin and testosterone concentrations in male polar bears (Ursus maritimus)

Seasonal changes in testicular size and serum LH, prolactin and testosterone concentrations in male polar bears (Ursus maritimus)