Male Fertility · Male Endocrine and Genetic Factors

Insulin Sensitivity and Testicular Function in a Cohort of Adult Males Suspected of Being Insulin-Resistant

Contreras PH, Serrano FG, Salgado AM, Vigil P

Published July 13, 2018 Frontiers in Medicine, 5, 190
DOI 10.3389/fmed.2018.00190 PMID 29998109 PMC PMC6028607
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RRM Academy Synopsis

Insulin-resistant men had about twice the rate of low testosterone

Men with insulin resistance were about twice as likely to have low testosterone, a study of 141 men suspected of insulin resistance found. In this group, low testosterone occurred in about 32 of 100 insulin-resistant men and 15 of 100 men without it. Waist size flagged insulin resistance well in these men. It flagged low testosterone less well.

Key Findings

  • Among 141 men aged 18 to 80, 94 (66.66%) were insulin resistant and 37 (26.24%) had hypogonadism (low testosterone).
  • Low testosterone occurred in 30 of 94 insulin-resistant men (31.91%) and 7 of 47 men without insulin resistance (14.89%), a relative risk of 2.143.
  • Of the 37 men with low testosterone, 30 (81.08%) were also insulin resistant.
  • A waist over 99 cm predicted insulin resistance (AUROC 0.812); 89.74% of those men had it. A waist over 110 cm was a mediocre predictor of low testosterone (AUROC 0.640).
  • Normal weight did not rule out insulin resistance: 8 of the 15 normal-weight men (53.3%) had it. Among 66 obese men, 9 (13.6%) were not insulin resistant.

Interpretation

Each man had one insulin test and one testosterone blood draw, so the design shows association only. The men were chosen because clinicians already suspected insulin resistance, so the rates describe this selected group. They do not describe men in general. Testicular function meant testosterone and sex hormone-binding globulin. Sperm and fertility were not measured. AUROC rates how well a measure separates two groups, from 0.5 (chance) to 1 (perfect). The authors suggest abdominal obesity brings insulin resistance first and low testosterone years later, a sequence one measurement cannot test. They did not measure leptin, a possible link they raise only as speculation.

RRM Context

Restorative reproductive medicine looks for root causes in both partners. Male factor contributes to many couples' infertility. Here, insulin resistance and low testosterone clustered in the same men, and normal weight did not exclude insulin resistance. The study reports no semen results or pregnancies.

Abstract

A cohort of 141 males (18-80 yo, 42.9 ± 12.9) strongly suspected of being Insulin Resistant (IR) was prospectively studied by determining their insulin sensitivity (Pancreatic Suppression Test, PST) and testicular function (total testosterone and SHBG). The subjects were labeled as IR when the Steady State Plasma Glucose (SSPG) was ≥150 mg/dL and Non-Insulin Resistant (NIR) when SSPG was <150 mg/dl; similarly, the subjects were labeled as Hypogonadal (HYPOG) when total testosterone was ≤3.0 ng/mL and Eugonadal (EUG) when total testosterone was >3.0 ng/mL. Two out of three subjects turned out to be IR, while around one in four subjects were HYPOG. Contingency analysis indicated a significant interdependence between insulin resistance and hypogonadism (chi-square was 4.69, p = 0.0303). Age (>43 yo) predicted hypogonadism (AUROC 0.606, p = 0.0308). Twice as many HYPOG subjects were IR as compared with EUG subjects. Also, HYPOG subjects exhibited higher SSPG values as compared with EUG subjects. Statistically, neither Weight nor BMI predicted hypogonadism, while Waist Circumference (>110 cm) was only a mediocre predictor (AUROC 0.640, p = 0.009). SSPG (>224 mg/dL) on the other hand, was the best predictor of hypogonadism (AUROC 0.709, p = 0.002), outperforming Waist Circumference (half of the subjects with an SSPG >224 mg/dL were HYPOG). Age did not predict insulin resistance, while Weight (>99 kg), BMI (>29), and especially, Waist Circumference (>99 cm, AUROC 0.812, p < 0.0001) were all predictors of insulin resistance. Almost 90% of the subjects with a waist circumference >99 cm was IR. As a logical consequence of the selection criteria (various clues suggesting insulin resistance), most subjects with normal weight in this cohort were IR (53.3%) while 20% were HYPOG. On the other hand, 13.6% of the obese subjects were NIR, and 2 out of 3 of them were both NIR and EUG. In conclusion, Waist Circumference predicted both insulin resistance (>99 cm) and hypogonadism (>110 cm), suggesting that the first hit of abdominal obesity is insulin resistance and the second hit is male hypogonadism. Normal weight did not protect from IR, while a relevant proportion of obese subjects were NIR (with 2/3 being also EUG).

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By this author

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Male Fertility › Male Endocrine and Genetic Factors › Male Hormonal Axis
Ana M Salgado, Pilar Vigil, Patricio H Contreras
A Salgado, P Vigil, P Contreras
PMID 29998109 29998109 DOI 10.3389/fmed.2018.00190 10.3389/fmed.2018.00190 Contreras et al. 2018, Contreras 2018

Cite this article

Contreras, P. H., Serrano, F. G., Salgado, A. M., & Vigil, P. (2018). Insulin Sensitivity and Testicular Function in a Cohort of Adult Males Suspected of Being Insulin-Resistant. Frontiers in medicine, 5, 190. https://doi.org/10.3389/fmed.2018.00190