Male obesity, sex hormone levels and sperm count: progress in fertility research

27 Nov 2008
Male obesity, sex hormone levels and sperm count: progress in fertility research

Three papers recently published in the same issue of the journal Fertility and Sterility dig deep into the complexities of the relationship between male obesity and infertility. Two of the papers report new findings whilst the third is a literature review summarizing work done and trends which have emerged.

The link between female obesity and infertility is much better understood, but research into male infertility has increased in recent years. In their review of the literature, Dr Hammoud and colleagues of University of Utah School of Medicine, US, conclude that there is now good evidence for a link between obesity and decreased fertility in males. However, the precise nature of this link is complex, as the other two studies make clear.

A large study, conducted by Dr Anette Aggerholm and colleagues at Aarhus University Hospital in Denmark, found no association between obesity and semen quality. The study is a new analysis of data collected in five smaller studies at Aarhus University Hospital which all involved taking blood and semen samples from all participants as well as recording lifestyle information and a record of the men’s height and weight. The 2139 men who took part in Dr Aggerholm’s study ranged in age from 18 to 66 years old and nearly half were overweight.

The researchers noted that levels of sex hormones were generally more decreased the more overweight a man was, and men who were moderately overweight had slightly lower sperm counts than men of average weight. However, obese men did not have lower sperm counts or sperm quality than men of an average weight. Dr Aggerholm concluded that, whilst there was a strong association between obesity and hormonal changes, if there is such an association between obesity and semen quality it was too small to be detected in this study. Although these findings are in direct contrast to a study conducted in 2004 by Dr Tina Jensen at Rigshospitalet, Denmark, Dr Aggerholm and colleagues suggest that this could be due to differing populations; Dr Jensen’s study recruited fewer obese males and took its sample from a generally younger population.

Dr Aggerholm’s team measured semen volume, sperm concentration, and sperm motility but did not measure DNA abnormalities of semen; previous studies (e.g. Kort et al., 2003) have shown that high BMI is associated with an increased rate of DNA fragmentation which, in turn, has been associated with reduced fertility. This may be an avenue for future investigation.

Dr Aggerholm’s study recorded levels of the sex hormones inhibin-B, follicle stimulating hormone, luteinizing hormone, testosterone, oestradiol and sex hormone-binding globulin. Work published in the same journal as Dr Aggerholm’s study in August this year by Dr Eric Pauli and his colleagues at Pennsylvania State University College of Medicine, US, also found that obese men had lower levels of most of these sex hormones in their blood. The much smaller study of only 87 men, who were recruited either because they were new fathers or because they were seeking fertility treatment due to their partners’ infertility, found that the more obese a man was, the lower his levels of hormones essential for reproduction. Dr Pauli and colleagues did not assess semen quality but suggest that hormonal changes could act to decrease a man’s fertility when acting in concert with dampened libido and increased risk of erectile dysfunction (both of which have been established by previous studies of male obesity).

It is important to note that the outcome measures in the studies summarized here are related to fertility but are not measuring conception success. Further studies are needed which investigate the links between male fertility measures, obesity and whether a couple achieve pregnancy or not. Additionally, Dr Hammoud and colleagues, authors of the review paper discussed, call for greater clinician awareness of the effects of male obesity on fertility as well as studies into the reversibility of obesity-associated male infertility with weight loss. Understanding the reason for this link could prove to be key in devising treatment strategies.

References

Aggerholm AS, Thulstrup AM, Toft G et al. 2008 Is being overweight a risk factor for reduced semen quality and altered serum sex hormone profile? Fertility and Sterility 90, 619–626.

Hammoud AO, Gibson M, Peterson M et al. 2008 Impact of male obesity on infertility: a critical review of the current literature. Fertility and Sterility 90, 897–904.

Jensen TK, Andersson AM, Jorgensen N et al. 2004 Body mass index in relation to semen quality and reproductive hormones among 1,558 Danish men. Fertility and Sterility 82, 863–870.

Kort HI, Massey JB, Witt MA et al. 2003 Sperm chromatin integrity is related to body mass index: Men presenting with high BMI scores have a higher incidence of sperm DNA fragmentation. Fertility and Sterility 80, S232–S232.

Pauli EM, Legro RS, Demers LM et al. 2008 Diminished paternity and gonadal function with increasing obesity in men. Fertility and Sterility 90, 346–351.

RB 2008/4064