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Human Reproduction, Vol.30, No.11 pp. 2587– 2596, 2015
Advanced Access publication on September 6, 2015 doi:10.1093/humrep/dev213
ORIGINAL ARTICLE Puberty, aging and HRT
Sexual dichotomy of gonadal function
in Prader – Willi syndrome from early
infancy through the fourth decade
H.J. Hirsch 1,2,*,†, T. Eldar-Geva 1,3,†, F. Bennaroch 4, Y. Pollak 1,5,
and V. Gross-Tsur 1,2,6,†
1
Neuropediatric Unit, Shaare Zedek Medical Center, Jerusalem 91031, Israel 2Department of Pediatrics, Shaare Zedek Medical Center, Jerusalem
91031, Israel 3Reproductive Endocrinology and Genetics Unit, Department of Obstetrics and Gynecology, Shaare Zedek Medical Center and The
Hebrew University School of Medicine, Jerusalem 91031, Israel 4The Herman Dana Child and Adolescent Psychiatry Unit, Hadassah-Hebrew
University Medical Center, Jerusalem 91031, Israel 5The School of Education, The Hebrew University, Jerusalem 91031, Israel 6The Hebrew
University School of Medicine, Jerusalem 91031, Israel
*Correspondence address. E-mail: [email protected]
Submitted on April 27, 2015; resubmitted on July 19, 2015; accepted on August 10, 2015
study question: At what age does the type of hypogonadism, namely hypothalamic or primary gonadal defect, become established in men
and women with Prader–Willi syndrome (PWS)?
summary answer: The type of hypogonadism becomes established only in late adolescence and early adulthood.
what is known already: The etiology of hypogonadism in PWS is heterogeneous and the clinical expression is variable. Primary testicular failure is common in PWS men, while combinations of ovarian dysfunction and gonadotrophin deficiency are seen in women.
study design, size, duration: This is a prospective study of a cohort of 106 PWS patients followed for a mean duration of 4.5 years.
Serial blood samples were obtained and assayed for gonadotrophins, inhibin B, anti-Mullerian hormone (AMH), dehydroepiandrosterone sulfate
(DHEAS), testosterone (males), and estradiol (females). Results were compared with normal reference values obtained from the literature. For
the purpose of this study, we defined the following age groups: infants ,1 year; children 1–10 years; adolescents 11– 20 years and adults .20
years.
participants/materials, setting, methods: Study participants were 49 males (aged 2 months to 36 years) and 57 females
(aged 1 month to 37 years) with genetically confirmed diagnoses of PWS (deletions 60, uniparental disomy 54, imprinting center defect 2) followed
in the Israel national multidisciplinary PWS clinic.
main results and the role of chance: Serum LH levels were in the normal range (1.0 – 6.0 mIU/ml) for 7/10 adult men, and
high in 3, while FSH (normal range 1.0 – 6.1 mIU/ml) was elevated (34.4 + 11.5 mIU/ml) in 6 and normal (3.5 + 1.6 mIU/ml) in 4 men. Testosterone was low (5.7 + 3.4 nmol/l) compared with the normal range of 12.0 – 34.5 nmol/l in the reference population in all men .20
years. AMH showed a normal decrease with age, despite low testosterone levels. Inhibin B was normal (241 + 105 pg/ml) in infant boys,
but low or undetectable in most adult men. Hormonal profiles were more heterogeneous in women than in men. Estradiol was consistently
detectable in only 7/13 adult women. Inhibin B was low or undetectable in all PWS females although occasional samples showed levels within
the normal range of 15 – 95 pg/ml. Vaginal bleeding was reported to occur for the first time in eight women at a median age of 20 years (13 – 34
years), but only one had regular monthly menses. The type of hypogonadism (primary or secondary) in PWS can be determined only after age
20 years.
limitations, reasons for caution: The study cohort was heterogeneous, showing variability in BMI, cognitive disability and
medical treatment.
wider implications of the findings: Demonstration of the natural history of reproductive hormone development in PWS
suggests that androgen replacement may be indicated for most PWS boys in mid-adolescence. Recommendations for hormone replacement
in PWS women need to be individually tailored, serial measurements of inhibin B should be performed, and contraception should be
considered in those women who may have the potential for fertility.
†
H.J.H., T.E.-G. and V.G.-T., contributed equally to this study.
& The Author 2015. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.
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Hirsch et al.
study funding/competing interest(s): This study was supported by grants from Pfizer Pharmaceuticals and from the Foundation for Prader – Willi Research. T. Eldar-Geva and V. Gross-Tsur received grant/research support funding from the Foundation for
Prader – Willi Research and from Pfizer Pharmaceuticals.
trial registration number: Not applicable.
Key words: Prader– Willi syndrome / delayed puberty / gonadotrophins / primary testicular failure / primary ovarian insufficiency / inhibin B /
anti-Mullerian hormone / hypogonadotrophic hypogonadism / hypergonadotrophic hypogonadism
Introduction
Hypogonadism is a major and prominent feature of Prader–Willi syndrome (PWS), a complex neurogenetic disorder characterized by hypotonia, onset of extreme weight gain and obesity in early childhood,
neuro-cognitive defects and behavioral disorders (Burman et al., 2001;
Crino et al., 2003; Goldstone et al., 2008; Cassidy and Driscoll, 2009;
Diene et al., 2010). Hypogonadism significantly contributes to poor
body image, muscle weakness, abnormal body composition, decreased
bone density and infertility in this syndrome. The etiology and expression
of hypogonadism varies among affected individuals. Hypogonadism in
PWS results from variable combinations of primary gonadal failure
along with hypothalamic dysfunction (Eiholzer et al., 2006; Hirsch
et al., 2009, 2013; Eldar-Geva et al., 2010a; Gross-Tsur et al., 2012;
Siemensma et al., 2012a,b).
Longitudinal studies of reproductive hormones in PWS have, to date,
focused on children and adolescents (Siemensma et al., 2012a,b), with
little or no data for individuals older than age 20 years. Since puberty
and age at menarche may be markedly delayed in PWS, information
regarding evolution of hormone patterns from adolescence into
adulthood is needed to understand the timing and tempo of hypothalamic –pituitary –gonadal (HPG) axis development in this syndrome. Longitudinal tracking of reproductive hormones in individual patients may
provide important data for understanding the natural history of the
HPG axis in PWS and lead to further refinement of treatment guidelines,
particularly with regard to determining when hormone replacement
should be initiated.
We performed a prospective study of reproductive hormones in
males and females with PWS from infancy through the fourth decade.
The aims of our study were to investigate when one can determine the
type of hypogonadism (hypothalamic or primary gonadal defect) in
PWS individuals, to observe if the type of hypogonadism remains
consistent for each individual, and assess the relative contributions of
hypothalamic versus gonadal dysfunction in a cohort of PWS patients
across a wide age range.
Methods
Patients
Study participants included 106 (49 males, 57 females) individuals (aged 1
month to 37 years) with PWS who were followed in our national multidisciplinary PWS clinic. Initial blood samples were obtained from 7 male and
9 female infants, 19 male and 30 female children, 13 male and 9 female adolescents, and 10 male and 9 female adults. Two or more sequential blood
samples were obtained from 10 males and 13 females after age 20 years.
This cohort includes nearly all known PWS individuals in Israel. Data from
the first sample drawn from these patients were described in previous
reports from our group, but sequential data have not yet been published
(Hirsch et al., 2009, 2013, 2014; Eldar-Geva et al., 2010a; Gross-Tsur
et al., 2012). Genetic diagnoses were deletion (DEL) in 60, uniparental
disomy (UPD) in 44, and an imprinting center defect (IC) in 2. Forty-eight children aged 6 months to 17 years were treated with growth hormone (GH).
None of the adult patients received GH prior to or during the study.
During the study period, 28 patients received risperidone and/or selective
serotonin-reuptake inhibitors (SSRI). Nine were taking methylphenidate
and three received anticonvulsant medication (topiramate or valporate).
Of four individuals with diabetes mellitus, three were on insulin treatment
and one was taking metformin. Three others with hypothyroidism were wellcontrolled on l-thyroxine. None of the study participants were treated with
androgens or sex steroid replacement prior to or during the study period.
The study was approved by the institutional review board of Shaare Zedek
Medical Center. Signed informed consent was obtained from parents,
guardians or adult participants.
Between 2007 and 2013, blood samples for hormone determinations
were obtained on 2 – 6 occasions from each patient. Physical examination
at each visit was performed by a pediatric endocrinologist (H.J.H.) or gynecologist (T.E.-G.) and included height measured with a wall-mounted stadiometer, weight, and assessment of pubertal stage according to the
Tanner classification (Tanner, 1962). Data from the CDC-2000 North
American growth standards were used for the normal age-related ranges
of BMI (Kuczmarski et al., 2000).
Hormone measurements
Blood samples were assayed for serum levels of LH, FSH, total testosterone,
estradiol (E2), prolactin and thyroid-stimulation hormone (TSH) using the
DxI 800 immunoassay system (Beckman Coulter Instruments, Inc., USA).
Assay sensitivities were 0.1 IU/l, 0.1 IU/l, 0.35 nmol/l, 37 pmol/l, 0.5 ng/
ml, and 0.03 U/ml for LH, FSH, testosterone, E2, prolactin and TSH, respectively. For testosterone, the intra-assay coefficients of variation were ,20%
for a level of 1.74 nmol/l and ,10% for levels of 6.94– 34.7 nmol/l. For
E2, the intra-assay coefficients of variation (CV) were 6.3 – 15% for levels
≥147 pmol/l and 20% for levels ,147 pmol/l. Serum inhibin B and antiMüllerian hormone (AMH) concentrations were measured using highly
sensitive two-site enzyme-linked immunosorbent assays (ELISAs) (DSL,
Webster, TX, USA) and the assay sensitivities were 10 and 0.017 ng/ml, respectively. Inter- and intra-assay CVs were 15 and 7% for inhibin B and 8.7 and
5.3% for AMH, respectively. Beginning in 2011, inhibin B was assayed using
the GEN II ELISA kit (Beckman-Coulter). Results of inhibin B obtained using
the older assay were adjusted for comparison with values obtained in the
GEN II assay by using the formula ‘inhibin B value in old assay × 1.57 +
11.29 ¼ value for new assay’ as recommended by Kalra et al. (2010). Sex
hormone-binding globulin (SHBG) concentrations were measured using
immunochemiluminescence and IMMULITE (Siemens, Diagnostic Product
Corporation, Los Angeles, CA, USA). Assay sensitivity for SHBG was
0.02 nmol/l and inter- and intra-assay CVs were ,10%. For each hormone,
normal values for age were obtained from the literature (Esoterix Laboratory
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Reproductive hormones in Prader – Willi syndrome
We compared our findings with normal reference data from published
reports as described in the methods section. A two-tailed T-test was used
to compare hormonal levels in women with PWS who experienced spontaneous vaginal bleeding with those with no history of vaginal bleeding (IBM Statistical Package for the Social Sciences for Windows, Version 19.0, IBM Corp
Armonk, NY, USA). A value of P , 0.05 was considered significant.
Tanner stage 3 testes size was achieved in seven men, only three
reached Tanner stage 4, however most remained at Tanner stage 1.
Penile length (Fig. 2A) was within the normal reference range in infancy
and early childhood (Sun et al., 2002). Although some increase in
penis size did occur during adolescence, penile lengths were below the
normal limit in all adult men except for two whose phallic length was
minimally above the lower limit of normal.
Two PWS boys showed onset and progression of pubic hair (Fig. 2B)
prior to the normal mean age of 11.8 years (Sun et al., 2002). Progression
to Tanner stages 4–5 was often achieved only in late adolescence or early
adulthood.
Results
Pituitary hormones
services; Rey et al., 1993; Lee et al., 1996; Andersson et al., 1997; Sehested
et al., 2000; Jensen et al., 2004; Sørensen et al., 2007; Aksglaede et al.,
2010). Results of hormone data are presented as mean + SD.
Statistics
PWS males
Clinical features: BMI and sexual development
During childhood and adolescence, BMI was markedly elevated in most
PWS boys (Fig. 1). BMI increased in younger boys, but decreased in older
adolescents. Adult men had BMI values within the normal range, most
likely due to strict diet control and exercise routines in the residential
hostel. Undescended testes (bilateral in 34 and unilateral in 12) were
noted at birth in 46 of 49 PWS males (Table I). The mean age when orchiopexy was performed in 37 boys was 2.7 years. Three boys had spontaneous testicular descent. Testes remained small in almost all PWS men.
Figure 3A –C shows gonadotrophin and prolactin levels versus age in
PWS males. LH and FSH decreased from early infancy to the expected
low levels seen in prepubertal boys. In most PWS boys, FSH levels
began to increase by 8–10 years of age and LH levels began to rise at
age 12 –13 years. During adolescence, LH levels were in the normal
range, but FSH was increased in some adolescent boys. In the 10 adult
Table I Clinical description of study participants with
Prader–Willi syndrome (PWS).
PWS males
PWS
females
........................................................................................
Figure 1 BMI in Prader – Willi syndrome. BMI in 49 males (A) and 57
females (B) with Prader – Willi syndrome (PWS) according to age. The
solid gray lines indicate the upper (+2 SD) and lower (22 SD) limits of
normal, according to growth data from the Center for Disease Control
North American growth database (CDC-2000) (Kuczmarski et al.,
2000).
Number of participants
49
57
Genetic diagnosis
(DEL/UPD/IC)
27/21/1
33/23/1
Age range
2.8 months to
36 years
1 month to 37
years
Age (years) at first sample
(median, range)
7.8
(0.2– 32.4)
6.6
(0.1–31.8)
Duration of follow-up in years
(median and range)
4.8
(1.0– 6.2)
4.4
(0.8–5.9)
Number of blood samples taken
149
190
Samples per patient
(mean, median, range)
3.2, 3
(2– 5)
3.0, 3.4
(2–6)
Cryptorchidism at birth (%):
46/49 (93.8%)
Bilateral, n (%)
34/46 (73.9%)
Unilateral, n (%)
12/46 (26.1%)
Scrotal testes, n (%)
3/49 (6.1%)
*Number of boys who underwent
orchiopexy (%)
37/46 (80.4%)
Number of boys with spontaneous
descent of testes
3/46 (6.5%)
Age (years) at orchiopexy
(mean, median, range)
2.7, 2.0
(0.3– 7.0)
No. of women with spontaneous
vaginal bleeding
8
Age (years) at first reported
vaginal bleeding
(median, range)
20
(13.5– 34)
DEL, deletion; UPD, uniparental disomy; IC, imprinting center defect.
*Six boys with cryptorchidism had not yet undergone orchiopexy at the time of this
study, primarily because of their young age or because of other medical problems,
e.g. sleep apnea, which led to a delay in the surgery.
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Figure 2 Secondary sexual characteristics of the patients with PWS. Development of secondary sexual characteristics in 49 PWS males and 57 PWS
females, including penile length (A), pubic hair according to Tanner stage in males (B), Tanner stage for breast development in PWS females (C), and
pubic hair according to Tanner stage for PWS females (D). For penile lengths, the solid gray lines indicate the upper (+2 SD) and lower (22 SD) limits
of normal (Schonfeld and Beebe, 1942). The average ages for achieving Tanner stage 2 for pubic hair (B and D) and Tanner stage 2 for breast development
(C) are shown by the blank arrows. The average ages for achieving Tanner stage 5 for pubic hair (B and D) and Tanner stage 5 for breast development (C) are
shown by the solid arrows. Normal ages for achieving breast and pubic hair development are described in Sun et al. (2002).
men aged 20 –35 years, values of LH were normal in 7 and elevated in
3 samples. None of the adult men had LH levels below the lower
normal limit of 0.8 IU/l. Relatively little variation in LH levels was seen
in individual adult PWS men except for one 23 year-old whose LH
levels fluctuated between 12.7 and 0.8 IU/l despite FSH values which
were persistently elevated. After age 20 years, FSH was markedly high
(34.4 + 11.5 mIU/ml) in 6/10 men, but was normal (3.5 + 1.6 mIU/ml)
in the other four.
Three young boys had high prolactin levels, possibly due to stressful
venipunctures, however prolactin levels were normal in adolescent
males. Hyperprolactinemia was noted, however, in 10 adult PWS men
all of whom were receiving risperidone or SSRI medications.
TSH levels were normal except for one 4-year-old boy whose TSH
was 6.35 mIU/ml. For PWS males, the TSH level (mean + SD) was
2.07 + 1.03 (0.77 –5.14) mIU/ml.
qualitatively similar to the pattern seen in normal boys. Levels were
highest in early infancy and gradually declined to low levels by adolescence, remaining low throughout adulthood.
Inhibin B was in the normal range (241 + 105 pg/ml) in infant males
(,1 year) and fell to lower levels by 2 years (Fig. 4D). Some boys
showed a transient rise in inhibin B between ages 9 and 20 years, but
levels were low to undetectable in adults (65 + 58 pg/ml).
SHBG levels were in the normal range for young infants up until age 2
years (Fig. 4B). From 2 years until early adolescence, SBHG levels were
generally below the lower limit of normal. After age 15 years, levels
were again in the normal range and were slightly elevated in the two
oldest adult men, aged 31 and 36 years.
DHEAS levels were within the normal range in most PWS males at all
ages, but eight children and adolescent boys had high values (Fig. 4E).
Testicular hormones, SHBG and DHEAS
PWS females
Testosterone fell from the normal mini-puberty values in infant boys to
the low or undetectable range expected during childhood. Nine boys
aged 10–15 years had normal testosterone levels (2.2 + 2.7 nmol/l)
for their age, however testosterone was low (5.7 + 3.4 nmol/l) in all
10 men above age 20 years (Fig. 4A). Values for testosterone were
relatively stable in all adults older than age 20 years.
AMH levels in men showed the expected decrease with age, despite
low testosterone (Fig. 4C). Although AMH levels in PWS were in the
lower half of the reference range, changes in levels with age were
Clinical features: BMI and sexual development
BMI values for young PWS girls were near or within the normal range,
increased as the girls entered adolescence, and were elevated in adult
women.
Three PWS girls began breast development before age 10 years
(Fig. 2C). One girl had Tanner 3 breasts and pubic hair at age 10 years
and a bone age of 11 –1/2 years. At age 12 years, her bone age was
14, however there was no progression of breast or pubic hair development and she had no menses. Subsequent to completion of this study,
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Reproductive hormones in Prader – Willi syndrome
Figure 3 Serum levels of pituitary hormones. Changes in pituitary hormone levels with age in 49 individual PWS males and 57 PWS females. For PWS
men, levels of LH, FSH and prolactin are shown in (A), (B) and (C) respectively. Levels of LH, FSH and prolactin for PWS women are shown in (D), (E) and
(F), respectively. The upper and lower limits of each hormone for a normal, reference population are indicated by the solid gray lines (Esoterix Laboratory
Services, Inc. http://www.esoterix.com/files/expected values.pdf; Hirsch et al., 2013).
another 7-year-old girl showed spontaneous onset of puberty. Most
women showed spontaneous progression of breast development, but
achievement of breast stage 5 generally occurred well past the normal
age of 15.5 years (Sun et al., 2002). Young PWS girls often had onset
of pubic hair prior to the normal age of 10.6 years (Fig. 2D). Most adolescent girls and adult women reached pubic hair Tanner stage 4–5.
Eight PWS women (5 DEL, 3 UPD) reported having spontaneous
vaginal bleeding (Table I). The median age for the first episode of
bleeding was 20 years with a range of 13.5 – 34 years. One woman
had regular monthly menses, but all others had oligomenorrhea or
secondary amenorrhea. The girl with vaginal bleeding at age 13.5
years had a BMI of 62.6 kg/m2, the highest BMI in our study. Mean
BMI for the other seven women with spontaneous bleeding was
37.9 kg/m2, similar to the BMI in amenorrheic PWS women. No differences in LH, FSH, inhibin B, or AMH levels were seen between
women who experienced vaginal bleeding compared with those
PWS women above age 12 years who did not. E2, however, was significantly higher in women who had at least one episode of bleeding compared with those who had none (185 + 146 versus 95 + 106 pmol/l,
P , 0.01).
Pituitary hormones
In females (Fig. 3D), LH and FSH were relatively high in infancy but
decreased to low levels in early childhood. LH remained low in most
of the young girls, with two exceptions. One 2-year-old girl had an LH
level of 15.6 mIU/ml which then fell to 1.3 mIU/ml. On further followup, LH levels in this girl remained above the age-related normal range.
Another girl had high LH levels ranging from 5.9 to 11.8 mIU/ml at
ages 6–10 years. LH was normal in adolescent girls. In adult women
over age 20 years, LH was normal in 6/13 (3.77 + 1.67 mIU/ml) but
low in 7/13 (0.21 + 0.18 mIU/ml). Sequential samples showed relatively little variation for individual PWS women .20 years, i.e. no crossover
between normal and low levels of LH was seen except for one
26-year-old with a low LH level whose levels subsequently increased
to within the normal range. Low LH levels were more common in
PWS women than in men.
FSH (Fig. 3E) was relatively high in PWS infant girls, similar to levels
seen in normal infants, but fell to the normal, lower values during childhood. One 15-year-old girl had a high FSH level which increased
further in repeated samples and subsequently showed a modest decrease. FSH levels in older adolescents and adults were generally in the
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Figure 4 Serum levels of testicular hormones, SHBG and DHEAS in 49 PWS males. Values obtained for serum testosterone (A), sex hormone-binding
globulin (SHBG) (B), anti-Müllerian hormone (AMH) (C), inhibin B (D) and dehydroepiandrosterone sulfate (DHEAS) (E) for individual PWS males are
shown in the respective panels. The solid gray lines show the upper and lower limits for a normal, reference population (Rey et al., 1993; Lee et al., 1996;
Andersson et al., 1997; Aksglaede et al., 2010; Hirsch et al., 2013; Josso et al., 2013).
normal range, although three PWS women had consistently low values.
In women aged 20 years or older, FSH was normal in 10/13 (6.42 +
3.78 mIU/ml) and low in three (0.71 + 0.60 mIU/ml).
Except for a 1-month old PWS infant girl whose TSH level was
7.2 mIU/ml, all other girls and women had normal TSH levels (1.87 +
1.06 mIU/ml).
Ovarian hormones, SHBG and DHEAS
E2 levels were in the normal prepubertal range of ,73 pmol/l in PWS
young girls and adolescents (Fig. 5A). E2 values were relatively low in
adult PWS women, although measurements in two women were
above the upper limit of normal for follicular phase levels. Only seven
adult women had E2 levels (157 + 133 pmol/l) consistently above the
lower limit of detection.
SHBG (Fig. 5B) levels in the PWS females were mostly within the
normal reference range, showing the expected decline from higher
values in infancy to lower values in childhood and adolescence. Levels
were slightly below the lower limit of normal in some PWS females
during childhood.
AMH (Fig. 5C) was below the normal median in most PWS females,
although high levels (3.67 + 2.66 ng/ml) were measured in seven girls
below age 12 years. Inhibin B (Fig. 5D) was low (19.6 + 16.8 pg/ml)
or undetectable in all PWS females.
DHEAS levels (Fig. 5E) were in the normal range for most PWS
women, although an early and exaggerated rise in DHEAS was seen in
Reproductive hormones in Prader – Willi syndrome
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Figure 5 Serum levels of ovarian hormones, SHBG and DHEAS in PWS females. Values obtained for serum estradiol (A), SHBG (B), AMH (C), inhibin B
(D) and DHEAS (E) for 57 individual PWS females are shown in the respective panels. Levels of DHEAS in PWS females are shown in (B). The solid gray lines
show the upper and lower limits for a normal, reference population (Esoterix Laboratory Services, Inc. http://www.esoterix.com/files/expected values.
pdf; Sehested et al., 2000; Sørensen et al., 2007).
seven PWS girls aged 5–9 years. Two women had DHEAS levels consistently above the upper limit of normal, but all other adult women had
levels in the normal range.
Discussion
This is the first study to report sequential changes in pubertal development and reproductive hormones including inhibin B, AMH, DHEAS
and SHBG, in a cohort of PWS individuals over a wide age-span from
early infancy into the fourth decade of adult life. The specific profile of
hypogonadism (hypothalamic versus primary gonadal dysfunction) in
each individual becomes apparent in late adolescence and early
adulthood in both sexes. Hormone patterns for each individual are consistent and stable after age 20 years.
Our findings for LH, FSH and testosterone confirm results reported in
our previous cross-sectional study (Hirsch et al., 2009), and are consistent with the longitudinal study on 68 PWS boys by Siemensma et al.
(2012a). Their study, however, included only two men older than
20 years and did not report results for prolactin, AMH, DHEAS or
SHBG. In their paper, one patient was diagnosed as having hypogonadotrophic hypogonadism at age 17 –8/12 years, but subsequently developed high gonadotrophin levels at age 24 years. We found that the
hormonal profiles typical of primary or secondary hypogonadism
become apparent only after age 20 years. For this reason, longitudinal
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follow-up of hormone levels into adulthood are needed in order to determine the type of hypogonadism for individual patients.
Our study is a representative cross-section of individuals with PWS,
including nearly all cases of this syndrome in Israel. Approximately 70%
of the adults live in one of several residential hostels. PWS individuals
who live in a hostel setting are more likely to maintain strict compliance
with a diet and exercise regimen and thereby avoid severe obesity, which
is more common in PWS individuals living at home with their families. We
obtained samples from PWS infants, children and adults. The wide age
range represented in our study clearly shows the decline in gonadotrophin, testosterone, and inhibin B levels from the ‘minipuberty’ values in
infancy, to low levels in childhood, followed by an increase in gonadotrophin levels in adolescents and adults. The low levels of testosterone
and inhibin B and very high levels of FSH in adult males demonstrate
that a primary testicular defect is the major contributor to hypogonadism
in PWS males. Although hyperprolactinemia, present in all PWS adult
men (most probably related to the use of SSRI medications), has an inhibitory effect on gonadotrophin secretion, nevertheless FSH was elevated. High FSH despite elevated prolactin provides additional support
to our findings of a primary testicular defect in this population.
Although cryptorchidism is a common feature in PWS (Crino et al.,
2003; Bakker et al., 2015a), we found that 3/49 boys had normally descended testes at birth and three others had spontaneous descent of undescended testes. Despite previous reports stating that micropenis is
common in PWS infants (Crino et al., 2003), we found that penile
length measurements were within the normal range during infancy and
early childhood (Fig. 2A). The normal ‘mini-puberty’ gonadotrophin
and testosterone levels found in PWS infant boys together with
normal penile lengths despite the high prevalence of undescended
testes, suggest that factors, other than hormones, are responsible for
the lack of testicular descent in these infants (Fillion et al., 2006; Hirsch
et al., 2013, 2014).
The age at puberty onset in our cohort is similar to that reported by
Radiocini who found that most PWS adolescent males experience the
onset of puberty but do not progress beyond Tanner stage 3 (Radicioni
et al., 2012). Testes were small in all of our PWS men, with only three
adults reaching Tanner stage 4 and none achieved Tanner stage 5 for
testes volume. Most adult men had penile lengths below the lower
limit of normal.
AMH levels showed a qualitatively normal decrease with age during
childhood, and were low in all PWS adult men. By contrast, AMH
levels are elevated in men with hypogonadotrophic hypogonadism
(Eldar-Geva et al., 2010b; Josso et al., 2013). The low intratesticular testosterone levels in our patients may be sufficient to inhibit AMH secretion by Sertoli cells, but not high enough to result in full pubertal
development or spermatogenesis. Alternatively, the low AMH levels in
PWS may indicate progressive deterioration in Sertoli cell function.
Our data showing that inhibin B levels were in the normal range
through adolescence, but were undetectable in nearly all adults older
than age 20 years (Hirsch et al., 2009) support the suggestion that
Sertoli cell function declines during or after puberty in PWS males. Testicular histology from PWS males showed decreased or absent spermatogonia (Vogels et al., 2008).
By age 15 years, testosterone levels were low suggesting that testosterone replacement might be appropriate as early as age 15 or 16
years, although careful monitoring of growth and skeletal maturation
would be needed to avoid deleterious effects on final height.
Hirsch et al.
Despite low levels of testosterone, AMH and inhibin B in PWS adult
males, we reported normal levels of insulin-like peptide-3, indicating
that testicular failure in PWS is not due to atrophic changes of entire
testes, but rather represents a specific and unique pattern of hypogonadism in PWS (Hirsch et al., 2013).
Most infants and children in our study were treated with GH, however,
none of the adults were treated with GH during or prior to the study.
Although it appears that GH treatment does not affect reproductive
hormones, particularly AMH, in children, some long-term effects are
possible. A recent study (Tinggaard et al., 2014) found no changes in
gonadotrophins and ovarian steroids in 18 short pre-pubertal, small
for gestational age (SGA) girls following up to 3 years of GH treatment.
AMH levels and ovarian volumes increased, but the differences were not
significant compared with findings in SGA girls who had not received GH.
Other studies found no direct effect of GH on AMH levels in Turner
syndrome (Visser et al., 2013), SGA boys (Boonstra et al., 2008), or in
SGA girls (Lem et al., 2011). Hypogonadism in PWS females is more
heterogeneous than in males and is characterized by low E2, normal
AMH, but very low or undetectable levels of inhibin B. Gonadotrophin
levels are generally in the normal range. As for PWS infant males, LH
and FSH were in the minipuberty range for PWS infant females and
levels decreased in early childhood.
Many of the PWS women in our study achieved full, Tanner stage 5
breast development. Most were amenorrheic, but eight women did
have at least one episode of vaginal bleeding, although the median age
was 20 years (range 13– 34 years). In the study by Siemensma et al., 5
of 61 PWS girls had menarche at ages ranging from 12 years to 16.5
years (Siemensma et al., 2012b), however, only one patient was followed
beyond 19 years of age. One of these women continued to have regular
menstrual periods, while two had oligomenorrhea and the other two had
secondary amenorrhea. Nevertheless, vaginal bleeding in PWS obese
adolescent or adult women may not indicate normal ovarian function
or true menarche, but more likely is due to unopposed estrogens of
adipose tissue origin.
Measurement of serum inhibin B levels may be important for management of adult PWS women. Inhibin B levels in individual women showed
considerable variability with levels ranging from undetectable to values
within the normal range. Women whose inhibin B levels are within the
normal range may have potential for fertility, and contraception may
be indicated for this subgroup of PWS women (Eldar-Geva et al.,
2013). Since inhibin B levels in individual women are variable, recommendations for treatment should be made only after the results of multiple
samples are available.
Although precocious puberty is uncommon in PWS, several case
reports have been published (Crino et al., 2008; Pusz and Rotenstein,
2008; Lee and Hwang, 2013). In our cohort, one 10-year-old girl had
rapidly advancing puberty, but by age 17 years she was still premenarchal.
Mutations in MKRN3, an imprinted gene located in the critical PWS
region of chromosome 15, have recently been shown to be associated
with familial precocious puberty (Abreu et al., 2013). Most PWS individuals, however, have delayed or incomplete pubertal development.
In conclusion, we described the development of reproductive
hormone patterns in PWS males and females. The type of hypogonadism
(hypothalamic versus primary gonadal dysfunction) becomes apparent
only in late adolescence and early adulthood in PWS men and women.
Hormonal profiles are stable for each PWS individual after age 20 years.
Primary gonadal dysfunction is a major component of hypogonadism in
Reproductive hormones in Prader – Willi syndrome
PWS, particularly in men, who show a steadily progressive deterioration in testicular function. Our findings support recommendations
for earlier initiation of testosterone replacement in PWS adolescent
boys (Bakker et al., 2015b). Recognition of age-related changes in reproductive hormones is important for tailoring individualized recommendations for contraception or hormone replacement and
counseling.
Acknowledgements
We are grateful to Nava Badichi, BA, for administrative assistance in coordinating blood sampling and data analysis and to Nurit Algor, MSc, for
performing the laboratory tests.
Authors’ roles
H.J.H., T.E.-G. and V.G.-T. each participated in planning the study, examining the patients, analyzing the data and writing the manuscript. F.B. contributed by evaluating the patients and reviewing the manuscript. Y.P.
performed statistical analyses of the data and assisted in preparing the
manuscript.
Funding
This study was funded by grants from the Foundation for Prader-Willi Research and Pfizer Pharmaceuticals.
Conflict of interest
T.E.-G. and V.G.-T. received grant/research support funding from the
Foundation for Prader-Willi Research and Pfizer Pharmaceuticals.
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