ORIGINAL ARTICLE

IGF-1 levels are significantly correlated with patient-reported

measures of sexual function

AW Pastuszak, JS Liu, A Vij, O Mohamed, K Sathyamoorthy, LI Lipshultz and M Khera

Scott Department of Urology, Baylor College of Medicine, Houston, TX, USA

Growth hormone (GH) supplementation may help to preserve erectile function. We assessed

whether serum insulin-like growth factor 1 (IGF-1) levels, a surrogate for GH levels, correlate with

sexual function scores in 65 men who completed the Sexual Health Inventory for Men (SHIM) and

Expanded Prostate Cancer Index Composite (EPIC) questionnaires, and had serum IGF-1 and

testosterone levels determined. Median

s.d. IGF-1 level, SHIM and EPIC scores were 235.0

86.4,

19.5

8.7 and 56.4

28.3 mgml

, respectively. IGF-1 levels and total SHIM score correlate

significantly (

0.31,

0.02), as do IGF-1 levels and all individual SHIM question scores, and

IGF-1 levels and the sexual domain of the EPIC questionnaire (

0.30,

0.02). No correlation

was observed between IGF-1 levels and Gleason score, IGF-1 and testosterone level or SHIM score

and testosterone level. These data support a potential role for the GH axis in erectile function.

International Journal of Impotence Research

(2011)

23,

220–226; doi:10.1038/ijir.2011.31;

published online 14 July 2011

Keywords:

erectile dysfunction; growth hormone; insulin-like growth factor-1; late-onset

hypogonadism; testosterone

Introduction

The male sexual cycle is regulated by a complex

interplay between neuroendocrine, vascular and

genital systems, and dysregulation of these systems

can result in erectile dysfunction. The contributions

of both vascular insufficiency and genital micro-

structural abnormalities to erectile dysfunction have

been extensively studied, while the neuroendocrine

axes have only recently come under scrutiny in the

setting of male sexual function.

1,2

The aging process

is associated with a decline in serum testosterone

levels, which when present together with symptoms

of androgen deficiency is termed late-onset hypo-

gonadism (LOH).

The true prevalence of LOH

remains uncertain, although a recent report suggests

that LOH is present in 3.1–7.0% of men less than 70

years old, and up to 18.4% of men over the age of 70,

when using total testosterone levels

300 ng dl

and

symptomatic

hypogonadism

diagnostic

criteria.

Testosterone replacement in men with LOH has

been shown to ameliorate the symptoms of LOH and

results in improvements in erectile function without

significantly increasing the incidence of clinically

significant prostate cancer, although the mechanism

of this improvement in erectile function remains

incompletely

elucidated.

3,5,6

However,

does

appear that this mechanism involves both local

and central mechanisms.

7–13

Growth hormone (GH)

levels, like testosterone, are also known to decline in

an age-dependent manner.

This progressive de-

cline has long been assumed to be physiological,

although decline in GH secretion is associated with

reduced lean body mass and bone density, an

increased incidence of ischemic heart disease,

dyslipidemia and erectile dysfunction, clinical out-

comes that have also been observed in LOH.

15–21

An association between low GH levels and erectile

dysfunction

has

been

described

otherwise

healthy male subjects, and recent

in vitro

and

animal studies suggest that GH upregulates nitric

oxide (NO) and may thus help to maintain erectile

function.

20,22–24

The downstream effects of growth

hormone are thought to be mediated in part by

insulin-like growth factors 1 and 2 (IGF-1,-2),

secretion of which is upregulated by GH. Given that

the half-life of IGF-1 (12–15 h) is significantly longer

than that of GH (less than 20 min), IGF-1 is consi-

dered to be a superior serum marker of growth

Received 26 August 2010; revised 18 February 2011;

accepted 19 May 2011; published online 14 July 2011

Correspondence: Assistant Professor M Khera, Scott

Department of Urology, Baylor College of Medicine, 6620

Main Street, Suite 1325, Houston, TX, USA

E-mail: mkhera@bcm.edu

International Journal of Impotence Research (2011) 23,

220–226

2011 Macmillan Publishers Limited

0955-9930/11