Objective:
To examine the relationship of male obesity and reproductive function.

Design:
Observational study.

Setting:
Academic medical center.

Patient(s):
Eighty-seven adult men, body mass index (BMI) range from 16.1 to 47.0kg/m2 (mean=29.3kg/m2; SD=6.5kg/m2).

Intervention(s):
None

Main Outcome Measure(s):
Reproductive history, physical examination, inhibin B, FSH, LH, T, and unbound T levels, and semen analysis.

Result(s):
Body mass index was negatively correlated with testosterone (r=−0.38), FSH (r=−0.22), and inhibin B levels (r=−0.21) and was positively correlated with E2 levels (r=0.34). Testosterone also negatively correlated with skinfold thickness (r=−0.30). There was no correlation of BMI or skinfold thickness with semen analysis parameters (sperm density, volume, motility, or morphology). Inhibin B level correlated significantly with sperm motility (r=0.23). Men with paternity had lower BMIs (28.0kg/m2 vs. 31.6kg/m2) and lower skinfold thickness (24.7mm vs. 34.1mm) than men without.

Conclusion(s):
Obesity is an infertility factor in otherwise normal men. Obese men demonstrate a relative hypogonadotropic hypogonadism. Reduced inhibin B levels and diminished paternity suggest compromised reproductive capacity in this population (Fig 1).

Figure 1: (a) Testosterone level and bilateral arm skin fold thickness; (b) testosterone level and body mass index; (c) inhibin B level and body mass index; (d) FSH level and body mass index; (e) estrogen level and body mass index; (f) sperm motility and inhibin B level. Pauli. Male gonadal function and obesity. Fertil Steril 2008. (Reprinted from Pauli EM, Legro RS, Demers LM, et al. Diminished paternity and gonadal function with increasing obesity in men. Fertil Steril. 2008;90:346-351, with permission from the American Society for Reproductive Medicine.)
 

Figure 1: (a) Testosterone level and bilateral arm skin fold thickness; (b) testosterone level and body mass index; (c) inhibin B level and body mass index; (d) FSH level and body mass index; (e) estrogen level and body mass index; (f) sperm motility and inhibin B level. Pauli. Male gonadal function and obesity. Fertil Steril 2008. (Reprinted from Pauli EM, Legro RS, Demers LM, et al. Diminished paternity and gonadal function with increasing obesity in men. Fertil Steril. 2008;90:346-351, with permission from the American Society for Reproductive Medicine.)
Figure 1: (a) Testosterone level and bilateral arm skin fold thickness; (b) testosterone level and body mass index; (c) inhibin B level and body mass index; (d) FSH level and body mass index; (e) estrogen level and body mass index; (f) sperm motility and inhibin B level. Pauli. Male gonadal function and obesity. Fertil Steril 2008. (Reprinted from Pauli EM, Legro RS, Demers LM, et al. Diminished paternity and gonadal function with increasing obesity in men. Fertil Steril. 2008;90:346-351, with permission from the American Society for Reproductive Medicine.)