Endocrinology of the hypothalamic-pituitary-testicular axis with particular reference to the hormonal control of spermatogenesis

Adult Exposure to Di-N-Butyl Phthalate (DBP) Induces Persistent Effects on Testicular Cell Markers and Testosterone Biosynthesis in Mice

Studies indicate that phthalates are endocrine disruptors affecting reproductive health. One of the most commonly used phthalates, di-n-butyl phthalate (DBP), has been linked with adverse reproductive health outcomes in men, but the mechanisms behind these effects are still poorly understood. Here, adult male mice were orally exposed to DBP (10 or 100 mg/kg/day) for five weeks, and the testis and adrenal glands were collected one week after the last dose, to examine more persistent effects. Quantification of testosterone, androstenedione, progesterone and corticosterone concentrations by liquid chromatography-mass spectrometry showed that testicular testosterone was significantly decreased in both DBP treatment groups, whereas the other steroids were not significantly altered. Western blot analysis of testis revealed that DBP exposure increased the levels of the steroidogenic enzymes CYP11A1, HSD3β2, and CYP17A1, the oxidative stress marker nitrotyrosine, and the luteinizing hormone receptor (LHR). The analysis further demonstrated increased levels of the germ cell marker DAZL, the Sertoli cell markers vimentin and SOX9, and the Leydig cell marker SULT1E1. Overall, the present work provides more mechanistic understanding of how adult DBP exposure can induce effects on the male reproductive system by affecting several key cells and proteins important for testosterone biosynthesis and spermatogenesis, and for the first time shows that these effects persist at least one week after the last dose. It also demonstrates impairment of testosterone biosynthesis at a lower dose than previously reported.

Heterogeneity and Dynamics of Vasculature in the Endocrine System During Aging and Disease

The endocrine system consists of several highly vascularized glands that produce and secrete hormones to maintain body homeostasis and regulate a range of bodily functions and processes, including growth, metabolism and development. The dense and highly vascularized capillary network functions as the main transport system for hormones and regulatory factors to enable efficient endocrine function. The specialized capillary types provide the microenvironments to support stem and progenitor cells, by regulating their survival, maintenance and differentiation. Moreover, the vasculature interacts with endocrine cells supporting their endocrine function. However, the structure and niche function of vasculature in endocrine tissues remain poorly understood. Aging and endocrine disorders are associated with vascular perturbations. Understanding the cellular and molecular cues driving the disease, and age-related vascular perturbations hold potential to manage or even treat endocrine disorders and comorbidities associated with aging. This review aims to describe the structure and niche functions of the vasculature in various endocrine glands and define the vascular changes in aging and endocrine disorders.

Male infertility due to testicular disorders

CONTEXT

Male infertility is defined as the inability to conceive following 1 year of regular unprotected intercourse. It is the causative factor in 50% of couples and a leading indication for assisted reproductive techniques (ART). Testicular failure is the most common cause of male infertility, yet the least studied to date.

EVIDENCE ACQUISITION

The review is an evidence-based summary of male infertility due to testicular failure with a focus on etiology, clinical assessment, and current management approaches. PubMed-searched articles and relevant clinical guidelines were reviewed in detail.

EVIDENCE SYNTHESIS/RESULTS

Spermatogenesis is under multiple levels of regulation and novel molecular diagnostic tests of sperm function (reactive oxidative species and DNA fragmentation) have since been developed, and albeit currently remain as research tools. Several genetic, environmental, and lifestyle factors provoking testicular failure have been elucidated during the last decade; nevertheless, 40% of cases are idiopathic, with novel monogenic genes linked in the etiopathogenesis. Microsurgical testicular sperm extraction (micro-TESE) and hormonal stimulation with gonadotropins, selective estrogen receptor modulators, and aromatase inhibitors are recently developed therapeutic approaches for men with the most severe form of testicular failure, nonobstructive azoospermia. However, high-quality clinical trials data is currently lacking.

CONCLUSIONS

Male infertility due to testicular failure has traditionally been viewed as unmodifiable. In the absence of effective pharmacological therapies, delivery of lifestyle advice is a potentially important treatment option. Future research efforts are needed to determine unidentified factors causative in "idiopathic" male infertility and long-term follow-up studies of babies conceived through ART.

Endocrine Tests and/or Testicular Volume are Not Predictive of Successful Sperm Retrieval by Conventional Multiple Testicular Sperm Extraction in Nonobstructive Azoospermia

Objectives: This study aimed to determine the role of presurgical markers in the prediction of sperm retrieval by conventional Multiple Testicular Sperm Extraction in infertile Vietnamese men with nonobstructive azoospermia (NOA).

Patients and Methods: Retrospective descriptive analysis of 136 infertile men with azoospermia, examined from August 2014 to July 2018. Patients underwent stepwise surgical sperm retrieval via percutaneous epididymal sperm aspiration, testicular sperm aspiration, then conventional multiple testicular sperm extraction in up to three locations, and procedures stopped as soon as sperm were detected. Factors were analyzed to determine the prediction of the likelihood of successful sperm retrieval, in men with NOA.

Results: The overall success rate of sperm retrieval in men with azoospermia was 49.3%, but it was only 18.4% in NOA group. The difference in testicular volume between men with successful sperm retrieval and unsuccessful sperm retrieval was not statistically significant in NOA group (5.68 ± 2.37 vs. 4.46 ± 2.83, p = 0.138). The differences in the endocrine tests between the two groups were also not significant in terms of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone (p [Formula: see text] 0.05). Multivariable analysis of predictive factors of sperm retrieval in NOA groups found no significant difference, except testicular density (p = 0.015).

Conclusions: In infertile men with NOA, neither an endocrine test nor testicular volume should be used for predicting the results of surgical sperm retrieval by conventional multiple testicular sperm extraction.

Kisspeptin and Testicular Function-Is it Necessary?

The role of kisspeptin in stimulating hypothalamic GnRH is undisputed. However, the role of kisspeptin signaling in testicular function is less clear. The testes are essential for male reproduction through their functions of spermatogenesis and steroidogenesis. Our review focused on the current literature investigating the distribution, regulation and effects of kisspeptin and its receptor (KISS1/KISS1R) within the testes of species studied to date. There is substantial evidence of localised KISS1/KISS1R expression and peptide distribution in the testes. However, variability is observed in the testicular cell types expressing KISS1/KISS1R. Evidence is presented for modulation of steroidogenesis and sperm function by kisspeptin signaling. However, the physiological importance of such effects, and whether these are paracrine or endocrine manifestations, remain unclear.

The REGγ-Proteasome Regulates Spermatogenesis Partially by P53-PLZF Signaling

Development of spermatogonia and spermatocytes are the critical steps of spermatogenesis, impacting on male fertility. Investigation of the related regulators benefits the understanding of male reproduction. The proteasome system has been reported to regulate spermatogenesis, but the mechanisms and key contributing factors in vivo are poorly explored. Here we found that ablation of REGγ, a proteasome activator, resulted in male subfertility. Analysis of the mouse testes after birth showed there was a decreased number of PLZF⁺ spermatogonia and spermatocytes. Molecular analysis found that REGγ loss significantly increased the abundance of p53 protein in the testis, and directly repressed PLZF transcription in cell lines. Of note, allelic p53 haplodeficiency partially rescued the defects in spermatogenesis observed in REGγ-deficient mice. In summary, our results identify REGγ-p53-PLZF to be a critical pathway that regulates spermatogenesis and establishes a new molecular link between the proteasome system and male reproduction.

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REGγ loss results in male subfertility

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REGγ loss results in a decrease of spermatocytes and PLZF⁺ spermatogonial cells

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p53 protein, increased in REGγ^−/− mouse testes, represses PLZF expression

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Allelic p53 haplodeficiency partially rescues defects in REGγ^−/− mouse spermatogenesis

Semen quality in patients with pituitary disease and adult-onset hypogonadotropic hypogonadism

OBJECTIVE

Gonadotropins (luteinizing hormone (LH) and follicle-stimulating hormone (FSH)) are released from the pituitary gland and stimulate Leydig cells to produce testosterone and initiates spermatogenesis. Little is known about how and when the deterioration of semen quality occurs in patients with adult-onset gonadotropin insufficiency.

DESIGN AND METHODS

A retrospective study comprising 20 testosterone-deficient men (median age, 29 years) with acquired pituitary disease who delivered semen for cryopreservation before initiation of testosterone therapy. Semen variables and hormone concentrations were compared to those of young healthy men (n = 340).

RESULTS

Thirteen of 20 patients (65%) and 82% of controls had total sperm counts above 39 million and progressive motile spermatozoa above 32% (P = 0.05). For the individual semen variables, there were no significant differences in semen volume (median (intraquartile range) 3.0 (1.3-6.8) vs 3.2 (2.3-4.3) mL, P = 0.47), sperm concentration 41 (11-71) vs 43 (22-73) mill/mL (P = 0.56) or total sperm counts (P = 0.66). One patient had azoospermia. Patients vs controls had lower serum testosterone 5.4 (2.2-7.6) vs 19.7 (15.5-24.5) nmol/L (P = 0.001), calculated free testosterone (cfT) 145 (56-183) vs 464 (359-574) pmol/L (P < 0.001), LH 1.5 (1.1-2.1) vs 3.1 (2.3-4.0) U/L (P = 0.002) and inhibin b (P < 0.001). Levels of FSH were similar (P = 0.63). Testosterone/LH ratio and cfT/LH ratio were reduced in patients (both P < 0.001).

CONCLUSIONS

Despite Leydig cell insufficiency in patients with acquired pituitary insufficiency, the majority presented with normal semen quality based on the determination of the number of progressively motile spermatozoa. In addition, the data suggest reduced LH bioactivity in patients with pituitary insufficiency.

Factors affecting spermatogenesis upon gonadotropin-replacement therapy: a meta-analytic study

A meta-analysis was performed to systematically analyse the results of gonadotropin and GnRH therapy in inducing spermatogenesis in subjects with hypogonadotropic hypogonadism (HHG) and azoospermia. An extensive Medline and Embase search was performed including the following words: 'gonadotropins' or 'GnRH', 'infertility', 'hypogonadotropic', 'hypogonadism' and limited to studies in male humans. Overall, 44 and 16 studies were retrieved for gonadotropin and GnRH therapy, respectively. Of those, 43 and 16 considered the appearance of at least one spermatozoa in semen, whereas 26 and 10 considered sperm concentration upon gonadotropin and GnRH, respectively. The combination of the study results showed an overall success rate of 75% (69-81) and 75% (60-85) in achieving spermatogenesis, with a mean sperm concentration obtained of 5.92 (4.72-7.13) and 4.27 (1.80-6.74) million/mL for gonadotropin and GnRH therapy, respectively. The results upon gonadotropin were significantly worse in studies involving only subjects with a pre-pubertal onset HHG, as compared with studies involving a mixed population of pre- and post-pubertal onset [68% (58-77) vs. 84% (76-89), p = 0.011 and 3.37 (2.25-4.49) vs. 12.94 (8.00-17.88) million/mL, p < 0.0001; for dichotomous and continuous data, respectively]. A similar effect was observed also upon GnRH. No difference in terms of successful achievement of spermatogenesis and sperm concentration was found for different FSH preparations. Previous use of testosterone replacement therapy (TRT) did not affect the results obtained with gonadotropins. Finally, a higher success rate was found for subjects with lower levels of gonadotropins at the baseline and for those using both human chorionic gonadotropin and FSH. Gonadotropin therapy, even with urinary derivatives, is a suitable option in inducing/restoring fertility in azoospermic HHG subjects. Gonadotropins appear to be more efficacious in subjects with a pure secondary nature (low gonadotropins) and a post-pubertal onset of the disorder, whereas previous TRT does not affect outcome.

Perfluorooctane sulfonate effects on the reproductive axis in adult male rats

Perfluorooctane sulfonate (PFOS) is a neurotoxic agent and it can disrupt the endocrine system activity. This work was undertaken to evaluate the possible effects of PFOS exposure on the hypothalamic-pituitary-testicular axis (HPT) in adult male rats, and to evaluate the possible morphological alterations induced by PFOS in the endocrine tissues of this axis. Adult male rats were orally treated with 0.5; 1.0; 3.0 and 6.0 mg of PFOS/kg/day for 28 days. After PFOS exposure, hypothalamic noradrenaline concentration increased in the anterior hypothalamus and in the median eminence, not changing in the mediobasal hypothalamus. PFOS treated rats presented a decrease of the gonadotropin releasing hormone (GnRH) gene expression, increasing the mRNA levels of the luteinizing hormone (LH) in rats treated with all doses administered except with the dose of 6 mg/kg/day. PFOS also induced a raise of the follicle stimulating hormone (FSH) gene expression in the animals exposed to 0.5 and 1.0 mg of PFOS/kg/day. After PFOS exposure, hypothalamic GnRH concentration was modified, LH and testosterone release was inhibited and FSH secretion was stimulated. Moreover, PFOS induced several histopathological alterations in the hypothalamus, pituitary gland and testis. The results obtained in the present study suggest in general terms that PFOS can inhibit the physiological activity of the reproductive axis in adult male rats, which could be explained, at least in part, by the structural alterations showed in the animals exposed to this chemical: very dense chromatin, condensed ribosomes and a loss of the morphology in the hypothalamus; a degeneration of the gonadotrophic cells, as well as a loss and degeneration of the spermatozoids and a very marked edema in the testis.

The relative roles of follicle-stimulating hormone and luteinizing hormone in maintaining spermatogonial maturation and spermiation in normal men

CONTEXT

Male hormonal contraception via gonadotropin and intratesticular androgen withdrawal disrupts spermatogenesis at two principal sites: 1) spermatogonial maturation, and 2) spermiation.

OBJECTIVE

The objective of this study was to explore the relative dependence of each stage of germ cell development on FSH and LH/intratesticular androgen action.

DESIGN, SETTING, AND PARTICIPANTS

Eighteen men enrolled in this prospective, randomized 14-wk study at Prince Henry's Institute.

INTERVENTIONS

Subjects (n = 6/group) were assigned to 6 wk of 1) testosterone (T) implant (4 x 200 mg sc once)+depot medroxy progesterone acetate (DMPA; 150 mg im once); 2) T implant+DMPA+FSH (300 IU sc twice weekly); and 3) T implant+DMPA+human chorionic gonadotropin (hCG; 1000 IU sc twice weekly as an LH substitute). Men then underwent a vasectomy and testicular biopsy with previously reported control data used for comparison.

MAIN OUTCOME MEASURES

Germ cell number (assessed by the optical disector stereological approach) and intratesticular androgen levels were determined.

RESULTS

T+DMPA alone significantly suppressed type B spermatogonia, preleptotene through to pachytene spermatocytes, and round spermatids from control (P < 0.05). All germ cell subtypes were maintained at control levels by either FSH or LH activity, except pachytene spermatocytes, which were found to be lower in the hCG vs. FSH (P < 0.01) and control groups (P < 0.05).

CONCLUSIONS

FSH and LH maintained spermatogenesis independently in this gonadotropin-suppressed model. Compared with LH, FSH showed better maintenance of pachytene spermatocyte number, whereas improved conversion to round spermatids was suggested with hCG treatment. Future contraceptive treatment strategies must consider independent regulation of spermatogenesis by both FSH and LH/intratesticular androgens for maximum efficacy.

Male germ line stem cells: from cell biology to cell therapy

Research using stem cells has several applications in basic biology and clinical medicine. Recent advances in the establishment of male germ line stem cells provided researchers with the ability to identify, isolate, maintain, expand and differentiate the spermatogonia, the primitive male germ cells, as cell lines under in vitro conditions. The ability to culture and manipulate stem cell lines from male germ cells has gradually facilitated research into spermatogenesis and male infertility, to an extent beyond that facilitated by the use of somatic stem cells. After the introduction of exogenous genes, the spermatogonial cells can be transplanted into the seminiferous tubules of recipients, where the transplanted cells can contribute to the offspring. The present review concentrates on the origin, life cycle and establishment of stem cell lines from male germ cells, as well as the current status of transplantation techniques and the application of spermatogonial stem cell lines.

The functional significance of FSH in spermatogenesis and the control of its secretion in male primates

The aim of this review is to provide an integrative analysis of the role of FSH in the control of testicular function in higher primates, including man. Attention is focused on the action of FSH during neonatal development, puberty, and adulthood. Whether FSH is the major determinant of the adult complement of Sertoli cells and whether FSH is obligatory for the initiation, maintenance, and restoration of spermatogenesis is evaluated. The mechanism whereby the circulating concentration of FSH regulates spermatogonial proliferation to dictate the sperm production rate under physiological conditions in the adult is discussed in detail. Inhibin B is the major component of the testicular negative feedback signal governing FSH beta gene expression and FSH secretion, and the evidence for this view is presented. The review concludes with the presentation of a model for the operation of the FSH-inhibin B feedback control system regulating sperm production postpubertally in monkey and man, and with speculation on issues of clinical interest.

Effects of simvastatin and pravastatin on gonadal function in male hypercholesterolemic patients

Inhibition of cholesterol biosynthesis by hydroxymethyl glutaryl coenzyme A (HMG-CoA) reductase inhibitors could, in theory, adversely affect male gonadal function because cholesterol is a precursor of steroid hormones. The objective of this randomized double-blind trial was to compare the effects of simvastatin, pravastatin, and placebo on gonadal testosterone production and spermatogenesis. After a 6-week placebo and lipid-lowering diet run-in period, 159 male patients aged 21 to 55 years with type IIa or IIb hypercholesterolemia, low-density lipoprotein (LDL) cholesterol between 145 and 240 mg/dL, and normal basal levels of testosterone were randomly assigned to treatment with simvastatin 20 mg (n = 40), simvastatin 40 mg (n = 41), pravastatin 40 mg (n = 39), or placebo (n = 39) once daily. After 24 weeks of treatment, mean total cholesterol levels were decreased 24% to 27% and mean LDL cholesterol was decreased 30% to 34% in the 3 active-treatment groups (P < .001 for all comparisons to placebo). At 24 weeks, there were no statistically significant differences between the placebo group and any of the active-treatment groups for the change from baseline in testosterone, human chorionic gonadotropin (hCG)stimulated testosterone, free testosterone index, follicle-stimulating hormone (FSH), luteinizing hormone (LH), or sex hormone-binding globulin (SHBG). Moreover, there were no statistically significant differences at week 12 or week 24 for the change from baseline in sperm concentration, ejaculate volume, or sperm motility for any active treatment relative to placebo. Both simvastatin and pravastatin were well tolerated. In summary, we found no evidence for clinically meaningful effects of simvastatin or pravastatin on gonadal testosterone production, testosterone reserve, or multiple parameters of semen quality.

High dose testosterone therapy for reduction of final height in constitutionally tall boys: does it influence testicular function in adulthood?

OBJECTIVE

We have studied the effect of treatment with high doses of androgens during puberty on testicular function in adult men with constitutionally tall stature, taking into account confounding factors interfering with sperm quality, since existing published data do not include whether testicular function is impaired by such treatment.

DESIGN

Historical cohort study.

PATIENTS

Forty-three previously androgen treated tall men (cases) and 30 non-treated tall men (controls).

MEASUREMENTS

Physical examination, semen analysis and plasma levels of LH, FSH, testosterone (T), sex hormone binding globulin (SHBG) and inhibin.

RESULTS

Sperm quality and testis volume were comparable between cases and controls. Mean sperm concentration was 66.4 x 10(6)/ml in cases and 66.2 x 10(6)/ml in controls. A left-sided varicocele was found in 45% of the cases and 37% of the controls. In cases we observed a significant effect of the age at start of androgen therapy on sperm motility (regr. coeff. (SE): 4.92 (2.41)%, P = 0.048). In addition, testicular size at start of therapy had a significant effect on sperm concentration (regr. coeff. (SE): 5.57 (1.54) x 10(6)/ml, P = 0.0012) and on total sperm count (regr. coeff. (SE): 43.1 (7.73) x 10(6), P = 0.0001). Plasma levels of T, SHBG and inhibin were not statistically different between the groups. Cases had significantly higher FSH levels (mean (SD) 3.3 (2.2) vs 2.1 (0.8) IU/I, P = 0.004) and significantly lower LH levels (mean (SD) 2.3 (0.9) vs 3.1 (1.4) IU/I, P = 0.019). We found a significant effect of age at start of therapy on plasma FSH level in the treated men (regr. coeff. (SE): -0.73 (0.18) IU/I, P = 0.0003).

CONCLUSIONS

Treatment with high doses of androgens for reduction of final height in constitutionally tall stature has no long-term side-effect on sperm quality, testicular volume or plasma testosterone levels. However, treated men had significantly higher plasma levels of FSH compared with controls. The meaning of this difference remains to be established. Varicocele was present in 42% of the adult tall men.

Effect of testosterone deprivation on expression of the androgen receptor in rat prostate, epididymis and testis

Adult rats were treated with ethane dimethane sulphonate (EDS) to eliminate the Leydig cells. This treatment resulted in very low levels of testosterone in the blood and in the testis. Furthermore, histological evaluation of spermatogenesis showed no marked differences between control and EDS-treated animals. In the ventral prostate, 5 days after EDS-treatment, a 4.0 +/- 0.3-fold up-regulation of androgen receptor (AR) mRNA was observed, together with a 2.2 +/- 0.2-fold increase in actin mRNA. In the epididymis, a 2.0 +/- 0.5-fold increase in AR mRNA level was observed, without a change in actin mRNA level. In the testes of EDS-treated rats, the AR mRNA level was not changed (1.02 +/- 0.17-fold of controls), and there was also no change in actin mRNA level at 5 days after EDS-treatment. These results indicate that AR mRNA expression in the ventral prostate and epididymis is regulated differentially by testosterone when compared to regulation in the testis. Testicular androgen binding sites were assayed by Scatchard analysis of the binding of 3H-R1881 to a nuclear fraction, that was isolated by a method which involved the use of liquid nitrogen and high sucrose buffer. The number of specific binding sites per testis in EDS-treated rats with testosterone-implants, remained unaltered compared to control rats (9.1 +/- 1.4 pmol/testis). In these rats, 20% of the normal testicular testosterone level was sufficient to maintain the androgen receptor in a tight nuclear binding (transformed) form. In testes from EDS-treated rats without testosterone-implants, the AR did not fractionate into the nuclear fraction; however, the total testicular AR content in these animals was close to control levels, as measured by nuclear 3H-R1881 binding after receptor transformation through injection of a high dose of testosterone (10 mg) 2 h before killing the rats (testosterone pulse). In the different experimental groups, FSH was not required to maintain the total testicular AR content (ligand binding). Immunoprecipitation and Western blotting of the testicular AR using specific monoclonal and polyclonal antibodies indicated that the total testicular amount of immunodetectable AR protein in long-term testosterone deprived rats was very low when compared to that in control rats or rats with testosterone-implants. This is in disagreement with results obtained in the ligand binding assay, and may point to a structural modification of the AR in the testis that possibly occurs in the prolonged absence of androgens.

Testosterone and FSH have independent, synergistic and stage-dependent effects upon spermatogenesis in the rat testis

Adult rats were hypophysectomized and treated with ethane dimethanesulphonate (EDS) selectively to eliminate the Leydig cells in the testis. By removing the source of endogenous gonadotrophins and androgens, the subsequent effects on the seminiferous epithelium were studied after 20 days of treatment with vehicle, or FSH (2 x 50 micrograms/day) or a low dose of testosterone (0.6 mg testosterone esters every 3rd day) alone or in combination. Compared to vehicle-treated hypophysectomized rats with Leydig cells, testis weight in saline-treated hypophysectomized rats treated with EDS declined by 50%, spermatogenesis was disrupted severely and only 18% of the tubules contained spermatids, these being confined to stages I-VI of the spermatogenic cycle. Treatment with either FSH or testosterone esters alone significantly (P less than 0.01) increased testis weight compared to vehicle-treated hypophysectomized rats treated with EDS and 40% of tubules contained spermatids either at stages I-VI after FSH, or at all stages I-XIV after testosterone treatment. Treatment with FSH and testosterone esters together maintained testis weights approximately 20% above vehicle-treated hypophysectomized controls; over 70% of the seminiferous tubules contained spermatids and there was a marked stimulation of spermatogenesis at all stages of the spermatogenic cycle. The results suggest, that in the absence of the pituitary gland and the Leydig cells, FSH alone partially supports spermatogenesis up to the development of round spermatids whereas testosterone is capable of maintaining spermatid development at all 14 stages of the cycle. When FSH and testosterone were administered in combination, the effects upon spermatogenesis were far greater than the response expected if their individual effects were simply additive. It is therefore concluded that FSH may play a role in normal spermatogenesis and that this role is essentially that of augmenting the response of the testis to testosterone. The biochemical mechanisms via which this might occur are discussed and hypophysectomized rats treated with EDS used in the present studies should provide a useful approach for their identification.

Semen quality and sex hormones among mild steel and stainless steel welders: a cross sectional study

Welding may be detrimental to the male reproductive system. To test this hypothesis, semen quality was examined in 35 stainless steel welders, 46 mild steel welders, and 54 non-welding metal workers and electricians. These figures represent a participation rate of 37.1% in welders and 36.7% in non-welding subjects. The mean exposure to welding fume particulates was 1.3 mg/m3 (SD 0.8) in stainless steel welders using tungsten inert gas, 3.2 mg/m3 (SD 1.0) in low exposed mild steel welders using manual metal arc or metal active gas (n = 31), and 4.7 mg/m3 (SD 2.1) in high exposed mild steel welders (n = 15). The semen quality of each participant was defined in terms of the mean values of the particular semen parameters in three semen samples delivered at monthly intervals in a period with occupational exposure in a steady state. The sperm concentration was not reduced in either mild steel or stainless steel welders. The sperm count per ejaculate, the proportion of normal sperm forms, the degree of sperm motility, and the linear penetration rate of the sperm were significantly decreased and the sperm concentration of follicle stimulating hormone (FSH) was non-significantly increased in mild steel welders. A dose response relation between exposure to welding fumes and these semen parameters (sperm count excepted) was found. Semen quality decreased and FSH concentrations increased with increasing exposure. Significant deteriorations in some semen parameters were also observed in stainless steel welders. An analysis of information from questionnaires obtained from the whole population including subjects who declined to participate indicated an underestimation of effects due to selection bias. Potential confounding was treated by restriction and statistical analysis. The results support the hypothesis that mild steel welding and to a lesser extent stainless steel welding with tungsten inert gas is associated with reduced semen quality at exposure in the range of the Danish process specific threshold limit values of welding.

Primary hypothyroidism and human spermatogenesis

Spermatogenic function was studied in 10 patients, previously diagnosed as having primary hypothyroidism, in whom a state of hypothyroidism has been induced by discontinuation or a decrease in treatment with levothyroxine over at least one spermatogenic cycle. Most of the patients had fathered children before the study. When the results obtained in the hypothyroid state were compared with those from a group of 16 controls with proven fertility, slight anomalies were observed; these were characterized by a decrease in seminal volume (p less than 0.05), progressive forward motility (p less than 0.01), and the cumulative percentage of mobile forms (p less than 0.01). There were no anomalies in sperm density or in the percentage of spermatozoa with normal morphology. No alterations in circulating levels of testosterone and gonadotropins existed. Induction of hypothyroidism did not lead to seminal or hormonal modifications compared with the same patients in a situation of euthyroidism. Short-term postpuberal hypothyroidism did not cause seminal alterations sufficiently intense to induce male infertility.

Quantitative parameters of seminiferous epithelium in secretory and excretory oligoazoospermia

Testicular biopsy specimens from infertile men (sperm count, less than 10(6)/ml) were evaluated on 1-micron thick sections, and counts of stem cells and differentiated spermatogonia, primary spermatocytes, early and late spermatids, and Sertoli cells were compared to counts in six fertile men. Biopsy specimens were also compared for the appearance of seminiferous tubule wall, blood vessels, and interstitium. Infertile men were grouped according to the following diagnoses: hypospermatogenesis (n = 5), spermatocyte arrest of spermatogenesis (n = 5), and obstruction of the genital tract (n = 7). A low productivity of spermatogenesis in cases of hypospermatogenesis appeared to be due to an exaggerated degeneration of primary spermatocytes and to a yield of abnormal spermatids. A block of meiosis in spermatocyte arrest was associated with a degeneration of primary spermatocytes and with a reduced number of staminal spermatogonia. Abnormal spermiogenesis was observed in cases of obstruction of the genital tract and was associated with an increase in stem cell spermatogonia. A thickening of seminiferous tubule and blood vessel walls could be responsible for the limited functional capacity of Sertoli cells, causing altered spermiogenesis in cases of excretory azoospermia. A severe primitive failure of Sertoli cells in secretory oligoazoospermia could account for a deranged maturation and degeneration of premeiotic and postmeiotic germ cells.