also shown that boys have a greater perineal length

than girls.

9,12–14

Investigators have also used AGD

to show that agents which disrupt androgen signal-

ing in animal models can lead to abnormal genital

length and even altered testicular function as mea-

sured by testosterone and sperm production.

15–18

In humans 2 recent studies have correlated AGD

in men to sperm production. A study of healthy male

volunteers demonstrated a positive relationship be-

tween anogenital distance and semen concentration,

motility and morphology.

Another study showed

that fertile men had greater anogenital length com-

pared to infertile men.

In addition, a similar pos-

itive association between anogenital length and

sperm count was identiﬁed. Assuming that AGD is

determined in utero, such studies suggest in utero

inﬂuences may impact genital development and

adult testicular function. To date, to our knowledge

no correlation of genital measures to hormone pro-

duction exists. As testicular and penile development

and function are related, we determined if human

androgen production is related to anogenital length.

METHODS

Study Population

The methods of cohort assembly have been previously

reported.

After obtaining institutional review board ap-

proval from Baylor College of Medicine, eligible patients

were recruited from a urology clinic specializing in repro-

ductive medicine from August 2010 through November

2010. Men with a history of orchiectomy, testicular torsion

or prior malignancy were excluded from study. A total of

116 men had serum hormone and genital measurements

available for analysis, including 89 evaluated for primary

infertility, 16 for secondary infertility, 8 for sexual dys-

function/hypogonadism and 3 for vasectomy. Mean age

SD was 36.1

8.0 years. Of the cohort 58.6% was white,

13.8% Hispanic and 13.8% black. All men provided writ-

ten consent for participation.

Genital Measurements

The methods of genital measurement have been described

previously.

In the supine, frog-leg position with the legs

abducted, allowing the soles of the feet to meet, the dis-

tance from the posterior aspect of the scrotum to the anal

verge was measured using a digital caliper (Neiko USA,

Model No. 01407A) (

ﬁg. 1

). The stretched penile length was

measured from the base of the dorsal surface of the penis to

the tip of the glans. When comparing measurements among

investigators the within subject standard deviation was 4.1

mm for anogenital distance and 5.4 mm for stretched PL.

The correlation coefﬁcient was 0.91 for AGD and PL mea-

surements. It is important to note that other investigators

have deﬁned anogenital distance from the anus to the ante-

rior base of the penis and the distance from the posterior

scrotum to the anus (as was measured in this study) as the

anoscrotal distance.

6,11,14

Given the age of the patients mea-

sured, the posterior scrotum was measured as the anterior

border as it was considered a more comfortable, reliable and

reproducible measure. Testicular volume was estimated

manually during the physical examination by 1 investigator

(LIL) at approximately 25 to 27C.

Hormone Analysis

All hormone assays were processed by a single, experi-

enced laboratory (Laboratory for Male Reproductive Re-

search and Testing, Baylor College of Medicine, Houston,

Texas). Testosterone (normal range 200 to 1,000 ng/dl), LH

(normal range 6 to 19 mIU/ml), FSH (normal range 4 to 10

mIU/ml) and estradiol (0.5 to 5 ng/dl) values were assessed

using an automated, 1-step competitive binding assay with

the Beckman Coulter Access® II Immunoassay system. The

assays were recalibrated daily with controls that spanned

the normal range for all hormones.

Statistical Analysis

ANOVA was used to compare means between groups. In

addition, the Wilcoxon rank sum test was also used given

the nonparametric distribution of the data with no differ-

ence in the overall interpretation or conclusions. Linear

regression models and correlation coefﬁcients were used

to determine the relationship between genital measures

and hormone values. Given the nonparametric distribu-

tion of the genital measures (ie AGD and PL), linear

regression models were also run with log

transformed

variables with no differences in the overall conclusions.

Linear regression coefﬁcients between genital measures,

hormone values and anthropomorphic variables were de-

termined, and relationships with p

0.2 were included in the

multivariable models. All p values were 2-sided and anal-

yses were performed using Stata® 10.

RESULTS

Anthropomorphic, hormonal and genital measure-

ments are listed in

table 1

. When stratifying by race

Figure 1.

Anogenital distance as measured with men in supine,

frog-leg position.

ANOGENITAL DISTANCE AND REPRODUCTIVE HORMONES

595