Human Reproduction, Vol.28, No.9 pp. 2343 –2349, 2013
Advanced Access publication on July 9, 2013 doi:10.1093/humrep/det286
ORIGINAL ARTICLE Andrology
Shorter anogenital distance correlates
with undescended testis: a detailed
genital anthropometric analysis in
human newborns
Viral G. Jain 1,2 and Arbinder Kumar Singal 2,3,*
1
Department of Paediatrics, MGM Medical College and MGM University of Health Sciences, Sector 18, Kamothe, Navi Mumbai, Maharashtra
410209, India, 2MITR Hospital & Hypospadias Foundation, Navi Mumbai, Kharghar, India and 3 Division of Paediatric Urology, MGM Medical
College and MGM University of Health Sciences, Kamothe, Navi Mumbai, Maharashtra, India
*Correspondence address. Tel/Fax: +91-22-27820520; Email: [email protected]
Submitted on March 6, 2013; resubmitted on June 8, 2013; accepted on June 13, 2013
study question: Are the anogenital distance (AGD) and stretched penile length (SPL) shorter in human newborn males with
cryptorchidism?
summary answer: AGD is significantly shorter in boys with undescended testis (UDT) and this correlation may indicate that both have a
common antecedent early in gestation.
what is known already: Animal studies have reported a critical time period during early gestation termed the male programming
window (MPW) where androgen deficiency results in reduced AGD and penile length, as well as cryptorchidism and hypospadias. Two pilot
human studies have explored this association but these studies were small and heterogeneous with regard to age, race and had selection bias.
study design, size, duration: A prospective descriptive study involving measurement of AGD and SPL at birth in a racially homogenous sample of 1154 consecutive newborns was performed over a period of 6 months. All measurements were taken by a single trained observer (V.J.).
participants/materials, setting, methods: All consecutively born male infants at a community hospital were classified as
having descended and or UDT. Testicular position in the undescended group was graded as high scrotal, inguinal or non-palpable. AGD (from the
centre of anus to the junction of the smooth and rugated skin of scrotum) and SPL were measured. The AGD index (AGDi) was calculated by
dividing AGD by cube root of birthweight.
main results and the role of chance: Of the 1154 infants examined, 624 were males and 71 had UDT. AGD was significantly
shorter in infants with UDT when compared with infants with descended testis (mean + SD; 2.21 + 0.36 versus 2.56 + 0.31 cm; P , 0.001).
AGDi was also significantly shorter in infants with UDT (mean + SD; 1.68 + 0.27 versus 1.81 + 0.20 cm/kg23; P , 0.001). Significance was
maintained even when preterm (P , 0.001) and low birthweight boys (LBW) (P , 0.001) were excluded. SPL was also significantly shorter
in infants with UDT (Mean + SD; 3.08 + 0.52 versus 3.31 + 0.38 cm; P , 0.001) but the significance was not maintained when preterm
(P ¼ 0.119) and LBW boys (P ¼ 0.666) were excluded. Birthweight, gestational age and length adjusted regression models showed significantly
shorter AGD in infants with UDT, but SPL was not different. Infants with higher position of testis appeared to have a shorter AGD and SPL but the
correlation did not reach statistical significance. No difference in AGD or SPL was noted between boys with unilateral and bilateral UDT.
limitations, reasons for caution: The present study did not include data pertaining to maternal or newborn health status. Also
parental drug exposure or occupational exposures to endocrine-disrupting chemicals was not studied. These may possibly affect genital anthropometric measurements.
wider implications of the findings: The study strengthens the hypothesis of existence of MPW in humans. Shorter AGD in
cryptorchid infants may reflect the effect of androgen disruption or deficiency during MPW. AGD may be a more reliable non-invasive marker
of androgen action during MPW than SPL to predict reproductive outcomes in humans.
study funding/competing interest(s): Supported by Hypospadias Foundation, India. The authors have no conflict of interest
to declare.
& The Author 2013. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.
For Permissions, please email: [email protected]
2344
Jain and Singal
Key words: anogenital distance / cryptorchidism / endocrine-disrupting chemicals / male programming window / testicular dysgenesis
syndrome
Introduction
An increase in the incidence of male reproductive disorders has been
reported in the past decade (Boisen et al., 2004; Boisen et al., 2005;
Virtanen and Toppari, 2008; Acerini et al., 2009). This has been attributed to a combination of lifestyle factors, prenatal exposure to environmental chemicals with endocrine-disrupting properties (Drake et al.,
2009; Main et al., 2009; Toppari et al., 2010; Virtanen and Adamsson,
2012) and genetic susceptibility (Boisen et al., 2004; Virtanen and
Toppari, 2008; Brouwers et al., 2012). However, some reports
suggest that the increase in the incidence of male reproductive disorders
may be due to changes in clinical practice which made their detection
more efficient (Thonneau et al., 2003; Thorup et al., 2010).
According to the concept of testicular dysgenesis syndrome (TDS),
various male reproductive disorders such as hypospadias, cryptorchidism, testicular germ cell cancer and low sperm counts may have a
common origin in early fetal life caused by an abnormality in testicular development (Sharpe and Skakkebaek, 2008; Main et al., 2010). Animal
studies have reported a critical time period, termed the ‘male programming window’ (MPW), during which genital development is programmed. This MPW is likely to be 8–14 weeks of gestation in
humans. Disruption of androgen action during the MPW has been
reported to result in altered anogenital distance (AGD) and penile
length as well as cryptorchidism and hypospadias (Welsh et al., 2008;
Drake et al., 2009; Macleod et al., 2010).
AGD is an anthropometric measure and a sensitive reproductive endpoint of masculinization in animals. AGD has been shown to be almost
twice as long in males when compared with females, both in animals as
well as humans (Gray et al., 1999; Salazar-Martinez et al., 2004; Thankamony et al., 2009; Sathyanarayana et al., 2010; Papadopoulou et al.,
2013). AGD has also been noted to serve as a potential biomarker for
various reproductive disorders in human studies (Hsieh et al., 2008;
Eisenberg et al., 2011; Mendiola et al., 2011; Castano-Vinyals et al.,
2012; Hsieh et al., 2012). Hitherto, only two pilot studies have reported
the relation of AGD with cryptorchidism in humans (Swan et al., 2005;
Hsieh et al., 2008). These studies were small and heterogeneous with
regard to age and race, and had selection bias. The present study aims
to explore the relation of various genital anthropometric correlates
with cryptorchidism in a large and racially homogenous cohort of consecutively born infants.
Materials and Methods
A prospective descriptive study measuring genital anthropometric variables
involving all consecutively born infants over a period of 6 months (February
2011 – August 2011) at a secondary level district hospital in Navi Mumbai,
India was performed. The hospital caters to a mixed urban and rural population from lower and lower-middle socio-economic classes. Infants born after
a complex, high-risk perinatal course were excluded from the study as they
were referred to tertiary care centres in the city. Infants with hypospadias,
chordee, anorectal malformation and other genito-urinary anomalies were
excluded from initial analysis. An informed consent was obtained from
parents of all study group infants. All families agreed to participate in the
study except one which refused for religious reasons. The study was
approved by the Navi Mumbai Municipal Corporation Hospital Ethics
committee.
Examination and classification of testicular position was performed using
standard techniques (Boisen et al., 2004). The study group consisted of
two groups: one with unilateral or bilateral cryptorchidism and a second
with descended testis. Boys with undescended testis (UDT) were further
classified into three subgroups according to the location of the UDT.
† High scrotal (HS): testes located at the upper part of the scrotum.
† Inguinal (IN): testes which are palpable somewhere along the line of
descent in the inguinal region, but are above the scrotum.
† Non-palpable (NP): UDT which were not palpable on external physical
examination.
If the infant had bilateral UDT, then the testis with the higher position of the
two was used for allocating the group.
Measurements
All the infants were examined by a single observer (V.J.) within the first 48 h
after birth. The examination began with recording of the testicular position,
then the stretched penile length (SPL) and finally the AGD as suggested by
Arbuckle et al. (2008). Three measurements each were taken for both
AGD and SPL and the average value was used in analysis.
Anthropometric parameters such as birthweight and body length were
measured using standard techniques. Gestational age was calculated using
antenatal ultrasound findings at 14– 20 weeks. If ultrasound report was not
available, last menstrual period date was used for calculating gestational
age. Maternal age and parity data were collected with the help of a structured
questionnaire.
For measuring AGD, the baby was put in a supine position with the hips
flexed and relaxed laterally by a family member or an attending nurse. The
distance from the centre of the anus up to the posterior base of scrotum
was measured (the junction of the smooth perineal skin and rugated skin
of the scrotum) in male infants (Salazar-Martinez et al., 2004; Thankamony
et al., 2009). Sliding vernier calipers which recorded length in increments of
0.1 mm was used for all measurements.
For measuring SPL, a wooden tongue depressor was used. The tongue depressor was placed at the penopubic junction and held with firm pressure.
The penis was gently stretched and held while the foreskin was gently
lowered. A mark was then made on the tongue depressor with a fine tip
pen corresponding to the tip of the penis (Romano-Riquer et al., 2007).
No attempt was made to forcibly retract the prepuce.
All measurements were done by a single observer (V.J.) to eliminate interrater variability. The observer was trained before the start of the study with
the examination of 43 newborn infants (26 males and 17 females) who were
randomly selected and not included in the final analysis. Six measurements
were taken for each of AGD and SPL; three at a time and repeated after
3 – 4 h. The observer was blinded and the results were read from the calipers
by the accompanying nurse. At the end of training period, the intrarater reliability of AGD was 93% for males and 90% for females, while it was 87%
for SPL.
Statistical analysis
All statistics were carried out using SPSS 16.0 (Chicago, IL, USA) with significance value set at P , 0.05. Student’s t-test or one-way ANOVA, followed
by Tukey’s post hoc test was used to compare the differences in means
2345
Anogenital distance and cryptorchidism in newborns
between groups. The Spearman correlation was used to study the strength of
association between genital measurements and testicular descent. Reliability
was calculated using a mixed effects model fitted to estimate the variance
components for AGD and SPL. Linear regression models were used to determine the relationship between genital measures and testicular descent.
Results
A total of 1185 births were registered in the hospital during the study
period, of which 1154 (97.4%) infants were examined by one of the
authors (V.J.). A total of 31 infants needed an emergency transfer to a
higher centre immediately after birth and hence were excluded. Of the
31 infants, 19 were males, which included 15 preterm. After excluding
infants with hypospadias and anorectal malformation, the final study
cohort comprised 1148 infants. Of these infants, 624 were males, of
which 553 had descended testis and 71 had cryptorchidism. The incidence of UDT in the whole study group was 71/624 (11.3%, 95% CI
9.12 –14.11), while it was 51/585 (8.7%, 95% CI 6.69 –11.28) in the
term infants and 36/481 (7.4%, 95% CI 5.45 –10.18) in the infants
with ≥2.5 kg birthweight. All infants were Asian Indians and 278 were
firstborn. Fifteen males were born of twin gestation and of these five
had UDT. The birthweight of the study group was comparable to regional
standards (Das et al., 2012). The mean birthweight, length, gestational
age and mother’s age of the study population are shown in Table I.
AGD and SPL were significantly correlated with each other (r ¼ 0.213,
P , 0.001).
AGD and SPL and correlation with UDT
The mean AGD was 2.21 cm in infants with UDT when compared with a
mean AGD of 2.56 cm in infants with descended testes (P , 0.001).
Further analysis after excluding the preterm infants or infants with low
birthweight (LBW), demonstrated that AGD was still significantly
shorter in infants with UDT (P , 0.001) (Table I).
Overall, SPL was also found to be significantly shorter in infants with
UDT when compared with those with a descended testes (3.08 cm
versus 3.31 cm, P , 0.001). However, when preterm infants or LBW
infants were excluded, SPL was not statistically different in infants with
UDT or descended testis (Table I).
Correcting AGD for birthweight
AGD index (AGDi) was calculated by dividing AGD by the cube root
of birthweight to account for body size effects (Gallavan et al., 1999).
We found that AGDi in infants with UDT was significantly shorter
than in infants with descended testis (1.68 + 0.27 versus 1.81 +
0.20 cm/kg23, P , 0.001). A significant difference was maintained
even after excluding preterm and LBW infants (Table I). Further analysis
of covariance (ANCOVA) using birthweight as a covariate to neutralize
the effect of birthweight on AGD showed that AGD continued to remain
shorter in boys with UDT (P , 0.001).
Multiple linear regression analysis was done to study the relationship
between testicular descent (descended ¼ 0 and undescended ¼ 1) and
AGD and SPL. AGD and SPL were found to be significantly shorter
in the UDT group infants in the unadjusted model (b ¼ 20.343;
95% CI ¼ 20.421 to 20.265; P , 0.001 and b ¼ 20.230; 95%
CI ¼ 20.329, 20.130; P , 0.001, respectively). However, after adjusting AGD and SPL for birthweight, gestational age and length; AGD continued to be significantly shorter in infants with UDT, while the difference
in SPL was not statistically significant (b ¼ 20.191; 95% CI 20.266
to 20.115; P , 0.001 and b ¼ 20.081; 95% CI 20.180 to 0.019
P ¼ 0.112, respectively).
Relation of AGD and SPL with position of testis
Within the subgroups of infants with UDT, even though we saw a negative correlation and a decreasing trend for both AGD as well as SPL with
higher testicular position (Table II), this did not reach a statistical significance. Further analysis of data using ANOVA showed no statistically significant difference in AGD [F(2,68) ¼ 1.697, P ¼ 0.191)] as well as SPL
[F(2,68) ¼ 1.721, P ¼ 0.187)] for the subgroups of UDT. A post hoc
Tukey test also did not reveal any statistically significant difference in
AGD as well as SPL for various positions (H.S., I.N. and N.P.) of UDT.
Relation of AGD and SPL with laterality
of UDT
Of the 71 children with UDT, 33 had bilateral UDT (46.4%). There was
no significant difference in AGD (2.23 + 0.36 versus 2.22 + 0.36 cm,
P ¼ 0.976) or SPL (3.28 + 0.53 versus 3.08 + 0.43 cm, P ¼ 0.064)
between infants with unilateral and bilateral UDT, respectively. Further
analysis with respect to the position of UDT and uni- or bi-laterality
also showed no significant difference in AGD or SPL (Table III).
Discussion
In the last decade, there have been many reports about the increasing
incidence of reproductive anomalies in humans. Endocrine-disrupting
chemicals (EDC’s) are often linked causally to this increasing incidence.
Among the reproductive disorders noted early in childhood, cryptorchidism is very common, and an increase in its incidence has been
reported (Boisen et al., 2004; Virtanen and Toppari, 2008; Acerini
et al., 2009). In the present study, the incidence of UDT is similar to
that reported by Boisen et al. (2004), but higher when compared to
other studies (Acerini et al., 2009; Ghirri et al., 2002; Thong et al.,
1998, Preiksa et al., 2005). An increasing trend in the incidence of
cryptorchidism is noted when compared with reports from previous
regional studies (Mital and Garg, 1972) (Fig. 1). Cryptorchidism has
been considered as a milder form of TDS while hypospadias, azoospermia and testicular germ cell cancer lie at the severe end of the
spectrum (Skakkebaek et al., 2001; Sharpe and Skakkebaek, 2008; Main
et al., 2009). AGD has been identified as one of the end-points in US
Environmental Protection Agency guidelines for reproductive toxicity
studies in animals (Arbuckle et al., 2008), and many animal studies have
shown that AGD, a marker of androgenization, is significantly shorter in
cryptorchid males (Welsh et al., 2008; Drake et al., 2009).
In the present study, we found that AGD is shorter in human infants
with cryptorchidism when compared with infants with descended
testis. To firmly test the correlation of AGD with UDT, we analysed
various models such as exclusion of preterm and LBW infants—correcting for birthweight by AGDi, ANCOVA and multiple regression models.
We confirmed that the correlation is unaffected by birthweight or gestational age signifying that a shorter AGD and testicular non-descent may
indeed have a common antecedent.
To date, only two studies have explored the relation of AGD with
cryptorchidism in humans (Swan et al., 2005; Hsieh et al., 2008).
However, these studies had selection bias and the cohorts were much
2346
Jain and Singal
Table I Parameters of the study group.
Parameters
All Babies
Testes
..............................................................
Descended
P value*
Undescended
.............................................................................................................................................................................................
All Infants
Birthweight (kg)a
2.77 (0.48)
2.83 (0.44)
2.33 (0.53)
Gestational age (weeks)b
39.1 (25.1– 42.4)
39.1 (32– 42.4)
37.4 (25 –41.2)
,0.01
48.8 (2.24)
46.7 (3.39)
,0.01
Length (cm)a
48.55 (2.48)
,0.01
Mothers age (years)b
24.8 (18– 42)
24.9 (18– 42)
AGD (cm)a
2.51 (0.33)
2.56 (0.31)
2.21 (0.36)
,0.001
AGDi (cm/kg23)a
1.80 (0.21)
1.81 (0.20)
1.68 (0.27)
,0.001
SPL (cm)a
3.28 (0.40)
3.31 (0.38)
3.08 (0.52)
,0.001
Total no.
624
553
Birthweight (kg)a
2.83 (0.42)
2.86 (0.41)
2.53 (0.38)
Gestational age (weeks)b
39.3 (37– 42.4)
39.3 (37– 42.4)
39.1 (37 –41.2)
24.38 (18 –40)
0.275
71
Infants ≥37 weeks of gestation
Length (cm)
a
,0.01
0.108
48.82 (2.17)
49.9 (2.13)
47.94 (2.45)
0.093
AGD (cm)a
2.54 (0.31)
2.57 (0.30)
2.25 (0.33)
,0.001
AGDi (cm/kg23)a
1.80 (0.20)
1.82 (0.19)
1.66 (0.22)
,0.001
SPL (cm)a
3.31 (0.38)
3.32 (0.38)
3.23 (0.42)
0.119
Total no.
585
534
Birthweight (kg)a
2.92 (0.32)
2.93 (0.32)
2.87 (0.26)
0.071
Gestational age (weeks)b
39.4 (35.4.1– 42.4)
39.4 (35.4– 42.4)
39.1 (36.4 –41.2)
0.126
51
Infants ≥2500 g birthweight
Length (cm)
a
49.37 (1.81)
49.39 (1.83)
49.11 (1.56)
0.382
AGD (cm)a
2.57 (0.31)
2.59 (0.29)
2.30 (0.35)
,0.001
AGDi (cm/kg23)a
1.79 (0.20)
1.81 (0.19)
1.64 (0.24)
,0.001
SPL (cm)a
3.34 (0.37)
3.34 (0.37)
3.31 (0.37)
0.666
Total no.
481
445
36
AGD, anogenital distance; SPL, stretched penile length; AGDi, anogenital distance index ¼ AGD divided by cube root of birthweight.
a
Mean (+SD).
b
Median (range).
*
P value: difference between groups of infants with descended and undescended testes.
smaller with different ages, races and urological diagnoses, which possibly
affected AGD. Swan et al. (2005) studied age group from 2–36 months
with the mean age of 15.9 months. That cohort had only 134 boys, and
14% of the boys had UDT. Hsieh et al. reported a small group of 109 boys,
of which 32 boys had UDT, but the boys in the group had varying ages
(mean: 47.4 months), racial compositions, body weights and genital anthropometry measured by multiple observers from two different
centres. The control group had only 47 boys, and all of these had
some urological anomaly. Exact positions of the UDT were also not mentioned in the study (Hsieh et al., 2008).
We have strengthened the present study by overcoming some of
these issues and biases. A single observer was adequately trained, a
large cohort of racially homogenous population was chosen at a single
district hospital, all consecutive newborns formed the study group and
all the measurements were taken within the first 48 h.
We also found that SPL is shorter in newborn infants with UDT when
compared with those with descended testis. However, after excluding
preterm and LBW infants or after adjusting for birthweight and gestation
age in linear regression analysis, the statistical significance was not
reached. This is in contrast to Acerini et al.’s findings where they found
a significantly shorter SPL in children with UDT at birth, though the
penile lengths ceased to be significantly different by 3 months of age. In
the present study, we attempted a more rigorous analysis by correcting
SPL for gestational age and birthweight and this may probably explain the
difference in results (Acerini et al., 2009).
Animal studies have shown that AGD, penile length, testicular descent
and hypospadias are influenced by androgen levels only during a critical
MPW, corresponding to 8–14 weeks of gestation in humans (Welsh
et al., 2008; Drake et al., 2009; Macleod et al., 2010). We also found
AGD and SPL to significantly correlate with each other in human newborns, thus indicating a possibility of common influence. While AGD is
established in the MPW, and grows proportionately with body growth
thereafter independently of androgen levels, SPL continues to be influenced by androgen levels even after the MPW later in gestation, and
post-natally until prepuberty (van den Driesche et al., 2011). Hence,
SPL may not be as sensitive a marker of androgen activity during MPW
as AGD. This is also corroborated by evidence in humans that penile
length correlates with androgen levels post-natally (Boas et al., 2006).
2347
Anogenital distance and cryptorchidism in newborns
Table II AGD and SPL measurements for various positions of testes.
AGD (cm)
....................................................................................
Descended
Undescended
.............................................................
High Scrotal
Inguinal
SPL (cm)
...................................................................................
Descended
Non-palpable
Undescended
.............................................................
High Scrotal
Inguinal
Non-palpable
.............................................................................................................................................................................................
All infants (n ¼ 624)
Mean
2.56
2.28
2.12
2.29
3.31
3.22
3.00
2.97
SD
0.31
0.30
0.35
0.49
0.38
0.48
0.53
0.57
Total
553
29
30
12
553
29
30
12
r ¼ 20.043, P ¼ 0.722
P value
r ¼ 20.252, P ¼ 0.034
Infants ≥37 weeks of gestation (n ¼ 585)
Mean
2.57
2.28
2.21
2.30
3.32
3.27
3.22
3.15
SD
0.30
0.28
0.32
0.52
0.38
0.43
0.35
0.59
Total
534
24
19
8
534
24
19
8
r ¼ 20.056, P ¼ 0.695
P value
r ¼ 20.153, P ¼ 0.283
Infants ≥2500 g birthweight (n ¼ 481)
Mean
2.59
2.31
2.23
2.42
3.34
3.39
3.26
3.22
SD
0.30
0.28
0.36
0.54
0.38
0.35
0.23
0.61
Total
445
18
12
6
445
18
12
6
r ¼ 20.220, P ¼ 0.197
P value
r ¼ 20.202, P ¼ 0.238
r ¼ correlation coefficient, within the subgroups of UDT, excluding descended testes. AGD, anogenital distance; SPL, stretched penile length; SD, standard deviation; UDT, undescended
testes.
Table III AGD and SPL in infants with uni- or bilateral UDT.
All UDT
....................................
Unilateral
Bilateral
High scrotal
....................................
Unilateral
Bilateral
Inguinal
.....................................
Unilateral
Bilaterala
Non-palpable
.....................................
Unilateral
Bilateralb
.............................................................................................................................................................................................
AGD (cm)
2.23
P value
0.976
SPL (cm)
P value
Total n
3.28
2.22
2.29
0.399
3.08
0.064
38
2.13
3.46
15
2.08
0.665
3.20
0.376
33
2.16
3.20
16
2.70
0.242
2.88
0.195
14
2.33
3.30
2.56
0.09
9
7
2
P value of difference between group of descended and UDT. AGD, anogenital distance; SPL, stretched penile length; UDT, undescended testes.
a
Excludes five cases where one testes was inguinal and other high scrotal in position.
b
Excludes one case where one testes was non-palpable and other high scrotal in position and two cases where one testes was non-palpable and other inguinal in position.
This may also explain why we found AGD to be significantly shorter in
boys with UDT, irrespective of birthweight or gestational age, while
SPL was not different once preterm and LBW infants were excluded. It
is possible that with advancing gestational age and subsequent incremental testosterone exposure, the penile length of term infants with UDT
approached normal levels.
Drake et al. (2009) suggested that increasing severity of UDT may be
associated with reduction in AGD in animals. Similarly in our study, AGD
and SPL appeared to be shorter with a higher testicular position;
however, this was not statistically significant. Since there are many
other factors which affect the final descent of testis, the severity as
decided by location of UDT may not be linearly correlated with AGD
measurements. The incidence of bilateral UDT (46.4%) in the present
study is similar to earlier reports (Preiksa et al., 2005; Acerini et al.,
2009). Interestingly, we did not find any significant difference in AGD
or SPL between bilateral and unilateral UDT groups.
Fetal testosterone levels are reported to be highest during early gestation (12–16 weeks) (Welsh et al., 2008; Thorup et al., 2010). We hypothesize that the trans-inguinal phase of testicular descent, which
occurs later in gestation in humans, may be dependent on (coded by) androgen levels during the MPW in early gestation. Also, uni or bi-laterality
of UDT may be independent of the severity of androgen disruption in
MPW and other factors such as genetic susceptibility may influence
this outcome. However, further studies with a larger sample size are
needed before any definitive conclusions can be drawn.
Recent human studies have shown decreased AGD after prenatal exposure to EDCs (Swan et al., 2005; Suzuki et al., 2012; Vafeiadi et al.,
2012), and their effect may be mediated through reduced prostaglandin
2348
Jain and Singal
multicentric longitudinal study based on genital anthropometry should
be done to better understand the long-term reproductive outcomes in
human populations.
Acknowledgements
Figure 1 Incidence of cryptorchidism in cohorts of infants with
gestational age ≥37 weeks.
(PG) synthesis leading to decreased testosterone levels (Kristensen et al.,
2011a). The use of PG synthesis inhibitors such as analgesics during first
and second trimester, specifically during 8–14 weeks of gestation, has
been linked to an increase in the incidence of cryptorchidism in newborns
(Jensen et al., 2010; Kristensen et al., 2011b). This time period is similar to
the MPW as inferred from animal studies. Thus, there is a possibility of
existence of a similar MPW during early gestation in humans where the
disruption of androgen influence may affect developing genitalia and
AGD may be a reliable marker of this effect.
In the current literature, various methods have been described for
measuring AGD; we measured ano-scrotal distance (ASD) as defined
by Salazar-Martinez et al. (2004). This measure has been found to be reliable in newborn studies and continues to be used in adults (Thankamony et al., 2009; Eisenberg et al., 2011; Papadopoulou et al., 2013).
In the present study, we only measured ASD and there may be a possibility that other AGD measures develop at different times of fetal growth.
Also, owing to the study design itself, other potential reasons of bias may
have been inclusion of all consecutive newborns irrespective of mothers
or infants health status, parental drug (analgesic) or occupational exposure to EDC. These factors may possibly affect AGD. However, we
believe that a large sample size would have mitigated these biases to a
minimum. We also did not obtain serum or urine samples to evaluate
extant biomarkers implying fetal exposure to EDC’s to correlate UDT
status, AGD and SPL directly with environmental factors. Finally, observer bias could not have been avoided as UDT was easily evident while
measuring the AGD.
Studies in adult men have shown that decreased AGD can be used to
predict testicular function, fertility, semen quality and prostate cancer
risk (Eisenberg et al., 2011; Mendiola et al., 2011; Castano-Vinyals
et al., 2012). Hence, it becomes important to study AGD longitudinally
and also determine various factors which affect AGD to better predict
adulthood reproductive outcomes.
Conclusion
The present study has shown that AGD is a potential reproductive biomarker in humans and is significantly shorter in children with UDT. AGD
may be clinically useful as a measure of androgen action during early gestation, and in this respect, it is a better measure than SPL. A large
We would like to acknowledge the contribution of Dr Richard Grady,
Program director, Pediatric Urology, Seattle Children’s Hospital, USA
for his help in ideation and conceptualization of this study. We would
also like to extend our thanks to Dr Rama Jayanthi, Chief, Pediatric
Urology, Nationwide Children’s Hospital, USA and Dr Aseem Shukla,
Director of Minimally Invasive Surgery, Division of Urology, The Children’s Hospital of Philadelphia, USA for help in preparing the manuscript.
We are also grateful for the support provided by Dr Savita Daruwalla,
Head of Pediatrics; Dr Prashant Jawade, Superintendent and the
nurses of Navi Mumbai Municipal Corporation Hospital, India for their
help in carrying out this study and Dr Pratap Jadhav, KEM Hospital,
Mumbai, India for statistical analysis.
Authors’ roles
V.J. was responsible for data collection, data analysis, data interpretation,
manuscript preparation and literature review. A.K.S. was responsible for
study design, data interpretation and critical manuscript review.
Funding
Supported by Hypospadias Foundation, India.
Conflict of interest
None declared.
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