This meta-analysis shows that bariatric surgery significantly improves sexual function in men but that a more limited degree of improvement is achieved in women.

In obese male patients who underwent bariatric surgery, the levels of the sex hormones TT, FT, LH, FSH, and SHBG significantly increased, and the level of E2 decreased. In obese female patients, the levels of the sex hormones TT, FT, and E2 decreased, but the levels of LH, FSH, and SHBG increased.

Future studies should be performed to elucidate the mechanism of the improved sexual function in obese patients after bariatric surgery.

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JOURNAL OF THE ENDOCRINE SOCIETY

Meta-Analysis

December 2017

Patients with a BMI >40, or >35 with serious coexisting medical conditions, are recommended to have bariatric surgery by the US National Institutes of Health. The effects of bariatric surgery on sexual function and sex hormone levels in obese patients were evaluated in this meta-analysis.

The PubMed, Medline, and Cochrane databases were searched for the terms bariatric surgery, sexual function, and sex hormone to identify adult human studies published in English. The search was restricted to dates between 1 January 1990 and 1 December 2016. Two investigators independently searched the literature according to the included and excluded criteria, extracted data, and evaluated the quality of data to perform a meta-analysis.

36 studies, including 1273 patients, met all criteria. The Female Sexual Function Index (FSFI) and the International Index of Erectile Function (IIEF) were used to measure female and male sexual function, respectively.

After surgery, the IIEF in obese men was significantly improved, but the FSFI in obese women was only slightly improved.

In obese male patients after bariatric surgery, the levels of total testosterone (TT), free testosterone (FT), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and sex hormone–binding globulin (SHBG) were increased, but the levels of estradiol (E2) were decreased.

In obese women, the TT, FT, and E2 were decreased, but the levels of LH, FSH, and SHBG were increased.

In conclusion, this meta-analysis indicated that bariatric surgery improves sex hormone levels and sexual function in men but only slightly improves them in women.

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Obesity is an increasing public health problem. In 2014, 15% of women and 11% of men aged ≥18 years were obese, as revealed in the Global Health Observatory data of the World Health Organization. The increasing prevalence of obesity is accompanied by comorbidities, such as diabetes, hypertension, heart disease, hyperlipidemia, and obstructive sleep apnea. In addition, obesity is also associated with sexual dysfunction and infertility. More than 50% of women with PCOS are overweight or obese. Moreover, obesity has been associated with changes in several sex hormones in women and men, which may reduce sexual function.

Lifestyle modifications, including diet and exercise, in obese patients have been shown to reduce diabetes and heart disease. However, one study indicated that most of the weight lost through diet and exercise in the majority of patients is regained in the long term. Bariatric surgery is another option that can achieve fast and lasting weight loss in obese patients, and bariatric surgery is associated with an improvement or resolution of obesity-related diseases. Patients with BMI >40, or >35 with serious complications, are advised to undergo bariatric surgery. Globally, the total number of bariatric surgeries increased from 344,221 cases in 2008 to 468,609 cases in 2013, and 95.7% of the procedures were laparoscopic.

The most commonly performed procedures are laparoscopic Roux-en-Y gastric bypass (LRYGB), laparoscopic gastric banding (LGB), laparoscopic adjustable gastric banding (LAGB), laparoscopic sleeve gastrectomy (LSG), Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG), adjustable gastric banding (AGB), gastric banding (GB), vertical gastric banding (VGB), biliopancreatic diversion (BPD), and silastic ring vertical gastroplasty (SRVG).

More than half of bariatric surgery patients have reported sexual dysfunction (SD). The Female Sexual Function Index (FSFI) and the International Index of Erectile Function (IIEF) are used to measure female and male sexual function, respectively. Women with a total FSFI score ≤26 are categorized as having female sexual dysfunction (FSD). Men who score <26 on the erectile function subscale are diagnosed as having erectile dysfunction (ED).

After bariatric surgery, insulin sensitivity is improved by weight loss, and sexual function is expected to improve. Some studies have shown that sexual function in obese patients is improved after bariatric surgery. However, one study has shown no improvement in sexual function after LGB, with deterioration of erectile index and orgasmic function when adjusted for time. Furthermore, a study has suggested that surgeons should be cautious about recommending bariatric surgery because the incidence of long-term complications after surgery is high, especially for laparoscopic gastric banding.

Some studies have found that obesity in men is associated with increased estrogens and reduced total testosterone (TT), free testosterone (FT), and sex hormone–binding globulin (SHBG) levels. Few studies have specifically evaluated the effect of bariatric surgery on sex hormone levels in obese patients, and the results are controversial. A randomized controlled trial investigated 10 obese men who accepted lifestyle interventions for 4 months and then underwent gastric bypass with a 20-month follow-up period. The study revealed that there was no impact on hormone levels or sexual function after lifestyle modifications but that TT, FT, and follicle-stimulating hormone (FSH) increased and estradiol (E2) decreased significantly after gastric bypass. Mora et al. found that TT, FT, FSH, and SHBG levels increased after GB and SG. In contrast, luteinizing hormone (LH) and E2 increased, but the increase did not reach statistical significance.

The relationships between bariatric surgery and type 2 diabetes mellitus (T2DM), hypertension, heart disease, and other diseases in obese patients have been given a great deal of attention. A meta-analysis found that 78% of 3188 patients with diabetes showed normalization of blood glucose after surgery. A meta-analysis indicated that obese patients experience improvement or resolution of their hypertension after bariatric surgery. In addition, a systematic review clearly illustrated a benefit of bariatric surgery not only on future cardiovascular risk but also on myocardial mass and diastolic function. A recent survey revealed that the number of patients who experienced an improvement in sexual dysfunction after surgery increases exponentially in both genders. Our meta-analysis aimed to obtain a global estimate of the effect of bariatric surgery on sexual function and sex hormone levels in obese patients.

Our meta-analysis showed that the IIEF in obese men and the FSFI in obese women improved after bariatric surgery, but the improvement was statistically significant only in men. These results were consistent with most current systematic reviews of changes in sexual dysfunction after bariatric surgery.

The current meta-analysis showed a significant increase in TT, FT, LH, FSH, and SHBG levels and a reduction in E2 levels after bariatric surgery in obese men.

In contrast, the TT and E2 levels in obese women significantly decreased, whereas LH, FSH, and SHBG levels significantly increased. The FT levels were also decreased in obese women, but these decreases were not significant.

The normalization of sex hormones may be one of the mechanisms contributing to the advantageous effects of surgery in morbid obesity patients.

The relationship between the improvement of sexual dysfunction and the sex hormone changes did not achieve consensus. Hammoud et al. found that changes in sex hormones and sexual function improve insulin resistance and inflammation, and they also reported that resolution of diabetes and hypertension occurs after RYGB. Our meta-analysis suggested that bariatric surgery is related to increased insulin sensitivity in both sexes, which may be one of the factors contributing to the improvement of sex hormone levels.

A previous study has reported that circulating testosterone in obese men increases after BPD, LGB, or AGB in parallel with a decrease in insulin resistance. However, no studies have reported the independent contribution of each factor. Ranasinghe et al. found that obese male patients displayed elevated TT, FT, and SHBG levels and improved IIEF scores but that erectile function scores were reduced after LGB, suggesting incomplete functional restoration. Relapsing obesity and recurring comorbidities might explain such an outcome. Two prospective cohort studies have shown no statistical evidence of the changes in FSFI and hormones after surgery by correlation of regression. However, a prospective observational study found that the increase in the IIEF score at 1 year after surgery was beyond the parallel improvement of hormone levels by a multivariate regression.

It is important to note that it is difficult to account for all risk factors that may contribute to sexual function, such as psychological factors and metabolic changes, when determining causality.

PCOS is a common endocrine disorder in women of reproductive age. A recent study has shown that surgically induced weight loss not only may reduce hirsutism in women but also may resolve menstrual and ovulatory dysfunction in severely obese patients with PCOS after bariatric surgery. Consistently, our meta-analysis showed sustained and marked weight loss after bariatric surgery with decreases in TT and FT levels, although FT levels only showed a trend, possibly because of the limited quantity of the included studies. These effects might also contribute to restoration of fertility in these women.

A previous study reported that weight loss by surgery may improve fertility rates in women, and it also suggested that pregnancy is delayed 1 to 2 years after bariatric surgery with proper nutritional and obstetric support. Significant increases in TT, FT, FSH, and SHBG levels have the potential to improve fertility in severely obese men. However, studies evaluating spermatogenesis after surgery have had inconsistent results. Some studies have suggested adverse effects on semen parameters, whereas some prospective studies have performed serial semen analyses and showed normal ranges for most parameters. A more recent study has shown that sperm concentration is increased in men with azoospermia and oligospermia after surgery, suggesting that weight loss may improve sperm quality.

Weight loss alone may be helpful in obesity-associated SD and is strongly recommended for the management of obesity. Lifestyle interventions that include diet and exercise have a short-term effect because weight loss is difficult to obtain by lifestyle modifications, and the weight is easily regained when the lifestyle interventions are not sustained. Bariatric surgery is a better and longer-lasting weight loss alternative for severely obese patients. Our meta-analysis indicated that bariatric surgery is associated with a greater increase in TT, FT, and SHBG levels and a greater decrease in E2 than lifestyle interventions in obese men. In obese women, however, our meta-analysis showed that levels of TT, FT, and E2 after bariatric surgery are more significantly decreased and that the levels of LH, FSH, and SHBG are more significantly increased in comparison with lifestyle modifications. These results may be caused by the greater weight loss achieved by surgery.

This meta-analysis was not without limitations. Several limitations that prevent achievement of definite conclusions should be considered.

First, there was significant heterogeneity in the outcome analyses, except for IIEF and FSH in men and E2 in women. This heterogeneity may result from the absence of randomized controlled trials, different research designs, and variable research populations.

Second, another limitation was the patient self-reporting, which was completed before and after surgery, because patients may have felt embarrassed when completing the sexual function questionnaires.

Third, our meta-analysis measured SD only by IIEF in men and by FSFI in women, but our meta-analysis did not include the Brief Male Sexual Function Inventory, which consists of an 11-item questionnaire. Also, our meta-analysis did not include the Impact of Weight on Quality of Life-Lite, which takes into account other aspects of self-esteem and work.

Fourth, the fact that hormonal assays and reference values often are not comparable imposed a limitation on the generalization of our results.

Fifth, we extracted the results at the 12-month time point only if parameters were evaluated at several different time points, which provided a conservative estimate of the effect of bariatric surgery on sexual function and sex hormones. The follow-up period after bariatric surgery in many studies was short, and the possibility of a relapse of obesity-associated sexual dysfunction and changes in sex hormone levels in the long term was not explored.

A limitation to this method was that the full effect of bariatric surgery on sexual function and sex hormones may not have been realized.

Finally, the small sample size of some studies was a limitation that especially affected the studies in women and the studies addressing the changes in sexual function after bariatric surgery.