Diminished paternity and gonadal function with increasing obesity in men

The impact of body mass index on semen parameters and reproductive hormones in human males: a systematic review with meta-analysis

BACKGROUND

It has been suggested that body mass index (BMI), especially obesity, is associated with subfertility in men. Semen parameters are central to male fertility and reproductive hormones also play a role in spermatogenesis. This review aimed to investigate the association of BMI with semen parameters and reproductive hormones in men of reproductive age.

METHODS

MEDLINE, EMBASE, Biological Abstracts, PsycINFO and CINAHL databases and references from relevant articles were searched in January and February 2009. Outcomes included for semen parameters were sperm concentration, total sperm count, semen volume, motility and morphology. Reproductive hormones included were testosterone, free testosterone, estradiol, FSH, LH, inhibin B and sex hormone binding globulin (SHBG). A meta-analysis was conducted to investigate sperm concentration and total sperm count.

RESULTS

In total, 31 studies were included. Five studies were suitable for pooling and the meta-analysis found no evidence for a relationship between BMI and sperm concentration or total sperm count. Overall review of all studies similarly revealed little evidence for a relationship with semen parameters and increased BMI. There was strong evidence of a negative relationship for testosterone, SHBG and free testosterone with increased BMI.

CONCLUSIONS

This systematic review with meta-analysis has not found evidence of an association between increased BMI and semen parameters. The main limitation of this review is that data from most studies could not be aggregated for meta-analysis. Population-based studies with larger sample sizes and longitudinal studies are required.

Insulin-like factor 3 as a marker of testicular function in obese men

OBJECTIVES

Testicular function declines with obesity as a result of central and peripheral mechanisms, including a primary dysfunction of the Leydig cells. The levels of insulin-like factor 3 (INSL3), a sensitive marker of Leydig cell impairment, have never been evaluated in obese men. To better evaluate the hormonal function of the testis in obese men, we analysed their INSL3 plasma levels and compared them with the obesity status and the other reproductive hormones.

DESIGN

Cross-sectional study.

PATIENTS

Thirty-one obese men [body mass index (BMI) >30 kg/m(2)) aged 22-49 years and 64 age-matched nonobese men.

MEASUREMENTS

Plasma concentrations of INSL3, testosterone (T), sex hormone-binding globulin (SHBG), oestradiol (E(2)), LH, FSH. Free testosterone (FT) levels were calculated.

RESULTS

Obese men had significantly lower plasma concentrations of total T, SHBG, FT and INSL3, and higher levels of E(2) with respect to nonobese men. LH and FSH values were not different from controls. In obese men, we found a significant negative correlation between BMI and INSL3, and a positive correlation between INSL3 and T. Only one (1/31, 3.2%) obese man had subnormal T levels. On the contrary, 10/31 (32.3%) obese men had low INSL3 values.

CONCLUSIONS

This study showed for the first time that INSL3 levels decrease with obesity, probably as a result of a primary dysfunction of the Leydig cells. INSL3 is a reliable marker of Leydig cell general impairment, whereas T mainly reflects the steroidogenic activity of these cells.

Abnormally high body mass index and tobacco use are associated with poor sperm quality as revealed by reduced sperm binding to hyaluronan-coated slides

Responses on a lifestyle questionnaire were correlated with results from traditional semen analysis and a newer functional sperm assay, namely, the ability of sperm to bind to a hyaluronan-coated slide. Increased percent normal morphology and motile sperm concentration were positively correlated with increased HA-binding score, whereas tobacco use (either current or previous history) and abnormally high body mass index were associated with lower binding scores.

Semen parameters and hormonal profile in obese fertile and infertile males

OBJECTIVE

To study the changes in semen parameters, gonadotropic and sex hormones, and serum leptin in obese fertile and infertile oligozoospermic men.

DESIGN

Prospective.

SETTING

University hospital.

PATIENT(S)

Forty-two obese fertile and 80 obese infertile oligozoospermic men (body mass index [BMI] >30).

INTERVENTION(S)

The BMI calculation, semen analysis, and serum FSH, LH, T, E(2), PRL, and leptin estimation.

MAIN OUTCOME MEASURE(S)

Semen and hormonal profiles.

RESULT(S)

Obese oligozoospermic patients had significant increase in mean BMI, serum FSH, LH, E(2), PRL, and leptin compared with obese fertile controls. The BMI had significant positive correlation with abnormal sperm morphology, LH, serum leptin and significant negative correlation with sperm concentration, sperm motility, serum T. Serum leptin demonstrated significant positive correlation with patients' age, abnormal sperm morphology, serum FSH, LH, PRL and significant negative correlation with sperm concentration, sperm motility, and serum T.

CONCLUSION(S)

Serum leptin mediates a link between obesity and male infertility.

Associations between andrological measures, hormones and semen quality in fertile Australian men: inverse relationship between obesity and sperm output

BACKGROUND

The World Health Organization developed a time to pregnancy (TTP) study (number of menstrual cycles taken to conceive) to determine whether the average TTP is increasing and semen quality decreasing with time. The present study describes clinical, semen and hormone characteristics obtained from male partners of pregnant women in Melbourne, Australia, and examines the associations between these characteristics.

METHODS

Male partners (n = 225) of pregnant women (16-32 weeks) who conceived naturally had physical examination, health and lifestyle questionnaires, semen and hormone (FSH, LH, sex hormone-binding globulin, testosterone and Inhibin B) analyses.

RESULTS

Previously known associations between semen, hormone and clinical variables were confirmed as significant: sperm numbers (concentration and total sperm count) correlated positively with Inhibin B and inversely with FSH and left varicocele, while total testicular volume correlated positively with sperm numbers and Inhibin B and inversely with FSH. However, only abstinence, total testicular volume, varicocele grade and obesity (BMI > 30 kg/m2) were independently significantly related to total sperm count. Compared with those with BMI < 30 (n = 188), obese subjects (n = 35) had significantly lower total sperm count (mean 324 versus 231 million, P = 0.013) and Inhibin B (187 versus 140 pg/ml, P < 0.001) but not FSH (3.4 versus 4.0 IU/l, P = 0.6).

CONCLUSIONS

Obese fertile men appear to have reduced testicular function. Whether this is cause or effect, i.e. adiposity impairing spermatogenesis or reduced testicular function promoting fat deposition, remains to be determined.

Semen quality and reproductive hormones according to birthweight and body mass index in childhood and adult life: two decades of follow-up

OBJECTIVE

To investigate the association between childhood body mass index (BMI), birth weight, and adulthood BMI, and adult semen quality and level of reproductive hormones.

DESIGN

Follow-up study.

SETTING

From a pregnancy cohort established in 1984-1987.

PATIENT(S)

347 out of 5,109 sons were selected for a study conducted 2005 to 2006.

INTERVENTION(S)

Semen and blood samples were related to information on BMI in boys (5-8 years), birth weight, and adult BMI.

MAIN OUTCOME MEASURE(S)

Semen characteristics and reproductive hormones.

RESULT(S)

Neither childhood BMI, birth weight, nor adulthood BMI were significantly associated with semen quality. Men with the 33% highest childhood BMI had 15% lower sex hormone binding globulin, 8% lower testosterone, and 16% lower FSH than men with the 33% lowest childhood BMI. Men with high adulthood BMI had 14% lower testosterone, 9% lower inhibin B, 31% lower sex hormone binding globulin, and 20% higher estradiol than men with low adulthood BMI.

CONCLUSION(S)

The results do not indicate an effect of childhood BMI, birth weight, or adult BMI on semen quality, but the exposure contrast in our study was limited. The hormonal status was affected by adult BMI.

Body mass index vis-à-vis total sperm count in attendees of a single andrology clinic

In this large series of 349 unselected men, no significant relationship between body mass index and total sperm count was found. Thus, the association of body mass index and sperm count reported in some studies was not confirmed.