Inhibin B and anti-Müllerian hormone/ Müllerian Inhibiting Substance may contribute
to the male bias in autism
Michael W. Pankhurst and Ian S. McLennan1
Supplementary Information
InhB and AMH can confound each other
InhB and AMH are both derived from the Sertoli cells of the testes, and the levels of
these hormones thus correlate in non-autistic boys 15 and in the current cohort of
autistic spectrum boys (Fig. S3, R=0.66). This implies that approximately 38% of
the variation of InhB and AMH relate to common influences, such as the number of
Sertoli cells in a boy’s testes. AMH and InhB have opposite effect on autistic traits
(Table 3 44). This will diminish the apparent relationship between each hormone
and the autistic traits, as 38% of the variation in each hormone relates to an
opposing affecter. For this reason, we suggest that the Sertoli cell hormones
should always be examined together, with their relative influences analysed using
linear regression models.
The correlates relate to the hormones and not the testes
InhB and AMH are used clinically to estimate Sertoli cell number, which is a
determinant of the size of the testes. The current observations do not link testes
size to autistic spectrum disorders, as InhB and AMH have opposing effects. The
levels of hormones are affected by their rate of production and release. Thus, it is
probable that the boy-boy variation in the levels of InhB and AMH relate in part to
the function of their testes. However, hormone levels are also influenced by the
half-life of the hormone in blood, which may vary between boys. Thus, the current
study only establishes a link between hormones (InhB/AMH) and autistic traits, and
does not prove that autistic symptoms are linked to the function of the testes, per
se.
When do the hormones act?
The current study examined 4- to 9-year-old boys, as the assessment of autistic
symptoms is difficult at a younger age. However, the autistic pathology begins at an
early age 2, and both InhB and AMH are present during the entire period of male
development 19, 21. Furthermore, the variation between boys is stable over time 15, 21.
It is therefore possible that the correlation between the hormones and autistic
symptoms arise because the levels of hormones in the boys reflect their levels at
earlier stages of development.
Do the hormones affect severity of symptoms?
The relationship between InhB and AMH and the ADI-R scores related to an effect
on the number of autistic traits rather than to the severity of the traits (Table 2).
Whilst this is correct for ADI-R scores and clinical diagnosis, it does not necessarily
Sertoli cell hormones and autism p1/5
imply that the severity of symptoms experienced by a boy is independent of his
Sertoli cell hormones. The power of regression analyses decrease when the scale
is compressed. The severity scale for each trait in the ADI-R is 0-3, with the
distinction between 2 and 3 being irregularly used: the scores of 2 and 3 are
included as “2” for clinical diagnosis 16. Consequently, the reported experiments
have a greater ability to detect associations with the breadth of symptoms than with
the severity of symptoms. This technical limitation notwithstanding, mild pathology
is more likely to be influenced by modulators, and the data as a whole is consistent
with this.
Girls with autistic spectrum disorders
AMH is profoundly dimorphic during development 19. However, Inhibin has two
isoforms, A and B, both of which are hormones. InhA has a female bias, whereas
InhB has a male bias. InhA and InhB have similar, but not identical activities 45, and
are expressed at different times in development (Fig. S1). Consequently, the
current study points to the need for InhA to be examined in girls
Direction of causality
The direction of causality cannot be determined from a correlation analysis. AMH
and InhB are both plausible regulators of brain development, suggesting that the
direction is hormone to brain. Alternatively, one function of hormones is to
transduce environmental influence on to physiological functions. We therefore do
not exclude the possibility that autistic pathology alters the levels of male hormones.
However, the behaviour of boys with an autistic spectrum disorder is highly
divergent from the general population, as is the growth trajectory of their brains.
Hence, if either autistic behaviour or growth trajectory regulates the levels of AMH
and InhB, then the levels of AMH and InhB should be different between autistic and
non-autistic boys. The current data is inconsistent with this possibility (Fig. 2),
although we note that the number of non-autistic boys in the current study is
insufficient to exclude a minor influence of autistic behaviour on hormone levels.
Figure S1. The pattern of gonadal hormones varies during development. The
levels of AMH (red line), inhibin B (Inhb, blue line) and testosterone (green line) are
dimorphic during development. 1The level of InhB in the plasma of women varies
considerably during the ovarian cycle. This figure is generated from multiple
sources, including references 19, 21, 38, 39, 42, 43, 46, 47.
Figure S2. A boy’s level of AMH does not correlate with his ADI-R scores. The
boy’s level of AMH was measured by ELISA and correlated with the scores for each
of the 3 ADI-R domains. The level of AMH was not significantly correlated with the
boy’s social score (A) R=0.07, n=82, (B) communication and language score (B)
R=0.09, n=63 or with his repetitive and stereotypic behaviour score (C) R=0.11,
n=82.
Figure S3. A boy’s level of AMH and InhB positively correlate. The levels of
AMH and InhB were measured by ELISA. The values for the non-autistic boys are
shown as black squares (n=16), with the data from autistic spectrum boys being
illustrated as green circles (n=82). The levels of AMH and InhB positively correlated
Sertoli cell hormones and autism p2/5
(R=0.66, p=0.000, n=82 for the autistic spectrum boys; R=0.66, p=0.006, n=16 for
the non-autistic boys).
44.
Pankhurst M, McLennan IS. Inhibin B and anti-Müllerian hormone/
Müllerian Inhibiting Substance may contribute to the male bias in
autism. Current Manuscript 2012.
45.
Brown CW, Houston-Hawkins DE, Woodruff TK, Matzuk MM. Insertion
of Inhbb into the Inhba locus rescues the Inhba-null phenotype and
reveals new activin functions. Nat Genet 2000; 25: 453-457.
46.
Chada M, Prusa R, Bronsky J, Kotaska K, Sidlova K, Pechova M et al.
Inhibin B, follicle stimulating hormone, luteinizing hormone and
testosterone during childhood and puberty in males: changes in serum
concentrations in relation to age and stage of puberty. Physiol Res
2003; 52: 45-51.
47.
Chada M, Prusa R, Bronsky J, Pechova M, Kotaska K, Lisa L. Inhibin
B, follicle stimulating hormone, luteinizing hormone, and estradiol and
their relationship to the regulation of follicle development in girls during
childhood and puberty. Physiol Res 2003; 52: 341-346.
Sertoli cell hormones and autism p3/5
Domain
SOC1T SOC2T SOC3T SOC4T COM1T COM2T COM3T COM4T BEHT1T BEHT2T BEHT3T BEH4T
SOC1T_CS 1.00
0.29
0.20
0.30
0.26
0.15
0.00
0.31
0.02
0.01
0.17
0.12
SOC2T_CS
1.00
0.31
0.32
0.33
0.37
0.00
0.41
0.03
0.07
0.14
0.10
SOC3T_CS
1.00
0.34
0.36
0.15
0.00
0.26
0.01
0.00
0.07
0.00
SOC4T_CS
1.00
0.40
0.24
0.00
0.42
0.00
0.01
0.37
0.05
COM1T_CS
1.00
0.20
0.03
0.39
0.00
0.00
0.11
0.01
COM2T_CS
1.00
0.00
0.16
0.04
0.02
0.12
0.21
COM3T_CS
1.00
0.02
0.09
0.14
0.04
0.05
COM4T_CS
1.00
0.00
0.00
0.27
0.01
BEH1T_CS
1.00
0.20
0.04
0.12
BEH2T_CS
1.00
0.04
0.21
BEH3T_CS
1.00
0.06
BEH4T_CS
1.00
Table S1. The ADI-R subdomains are measuring traits that are largely independent of each other.
The independence of the traits measured by each subdomain was examined using partial correlates. The values are correlation
coefficients (R2).
n
82
82
82
82
82
63
63
82
82
82
82
82
Sertoli cell hormones and autism p4/5
Figure S1. The pattern of gonadal hormones varies during development. The
levels of AMH (red line), inhibin B (Inhb, blue line) and testosterone (green line) are
dimorphic during development. 1The level of InhB in the plasma of women varies
considerably during the ovarian cycle. This figure is generated from multiple
sources, including references 17, 19, 34-39.
Figure S2. A boy’s level of AMH does not correlate with his ADI-R scores. The
boy’s level of AMH was measured by ELISA and correlated with the scores for each
of the 3 ADI-R domains. The level of AMH was not significantly correlated with the
boy’s social score (A) R=0.07, n=82, (B) communication and language score (B)
R=0.09, n=63 or with his repetitive and stereotypic behaviour score (C) R=0.11,
n=82.
Figure S3. A boy’s level of AMH and InhB positively correlate. The levels of
AMH and InhB were measured by ELISA. The values for the non-autistic boys are
shown as black squares (n=16), with the data from autistic spectrum boys being
illustrated as green circles (n=82). The levels of AMH and InhB positively correlated
(R=0.66, p=0.000, n=82 for the autistic spectrum boys; R=0.66, p=0.006, n=16 for
the non-autistic boys).
Sertoli cell hormones and autism p5/5