clinical significance of serum follistatin levels in the diagnosis of ovarian endometrioma and benign ovarian cysts

Taiwanese Journal of Obstetrics & Gynecology 54 (2015) 236e239

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Original Article

Clinical significance of serum follistatin levels in the diagnosis of
ovarian endometrioma and benign ovarian cysts
€
€
_
Omer
Ant, Gülnur Ozaks
¸ it, Ali Irfan
Güzel, Sabri Cavkaytar, Metin Kaba,
*
Hasan Onur Topỗu
Dr Zekai Tahir Burak Women's Health Education and Research Hospital, Department of Obstetrics and Gynecology, Ankara, Turkey

a r t i c l e i n f o

a b s t r a c t

Article history:
Accepted 17 March 2014

Objective: To determine the clinical significance of serum follistatin levels in women with an ovarian
endometrioma.

Materials and methods: This is a prospective study of 89 women, 56 with an ovarian endometrioma
(endometrioma group) and 33 with a benign ovarian cyst (control group) who underwent laparoscopic
excision. Age, parity, body mass index, serum CA-125, serum CA 19-9, and serum follistatin levels were
determined for all participants and evaluated as potential prognostic factors prior to laparoscopic
cystectomy.
Results: There were no significant differences in demographic factors between the endometrioma group
and the control group. However, serum follistatin levels were significantly higher in the endometrioma
group (9350 ± 895 pg/mL vs. control group 725 ± 72 pg/mL, p < 0.05). The optimal diagnostic cut-off values
(sensitivity and specificity) of CA-125, CA 19-9, and follistatin for ovarian endometrioma were 23.2 IU/mL
(82.14% and 72.73%), 30.14 IU/mL (45.28% and 87.50%), and 2350 pg/mL (53.7% and 60.61%), respectively.
Conclusion: Despite the increased serum follistatin levels in patients with ovarian endometrioma, CA125 was determined to be a more sensitive and specific marker than follistatin for the diagnosis of
ovarian endometrioma and endometriosis.
Copyright © 2015, Taiwan Association of Obstetrics & Gynecology. Published by Elsevier Taiwan LLC. All
rights reserved.

Keywords:
CA-125
CA 19-9
diagnostic marker
endometriosis
follistatin

Introduction
Endometriosis is a chronic condition characterized by the
growth of hormone-responsive endometrial tissue outside the
uterine cavity [1]. An ovarian endometrioma is a cyst composed of
endometrial tissue detected in 20e40% of women with endometriosis [1,2]. The gold standard for diagnosis of endometriosis is
histological examination, which requires an invasive procedure,
such as laparoscopy or laparotomy, to obtain tissue samples [3,4].
Many serum biochemical markers, such as cytokines, hormones,

and growth factors, which may be released into the bloodstream by
ectopic endometrial tissue, have been suggested for noninvasive
diagnosis of endometriosis. Although these markers have some
clinical value, diagnostic serum markers for endometriosis have not

* Corresponding author. Dr Zekai Tahir Burak Women's Health Education and
dem Mahallesi 1549, Cadde, Hardem
Research Hospital, Division of Gynecology, Çig
Apartmanı, B Blok, D:12, Çankaya, Ankara, Turkey.
E-mail address: (H.O. Topỗu).

been identied. CA-125, a transmembrane glycoprotein, is elevated
in women with endometriosis [5], and previous studies have reported that ectopic endometrial tissue may release follistatin into
the bloodstream [5e8].
Follistatin is an extracellular glycoprotein originally identified as
an inhibitor of pituitary follicle-stimulating hormone secretion. The
majority of follistatin's physiological effects are due to its ability to
neutralize activin [9,10]. Florio et al [11] reported that follistatin is
expressed in human endometrium and ectopic endometrial tissue,
and is a promising diagnostic marker due to its sensitivity and
specificity for ovarian endometriomas.
This study compares the serum levels of follistatin in women
with ovarian endometriomas with those with benign ovarian cysts
to determine the role of follistatin in the diagnosis of ovarian
endometrioma and endometriosis.
Materials and methods
This prospective case control study was conducted between
February 2012 and May 2013 at Zekai Tahir Burak Women's Health

/>1028-4559/Copyright © 2015, Taiwan Association of Obstetrics & Gynecology. Published by Elsevier Taiwan LLC. All rights reserved.

€ Ant et al. / Taiwanese Journal of Obstetrics & Gynecology 54 (2015) 236e239
O.

Education and Research Hospital in Ankara, Turkey. The study was
performed according to the standards of the Helsinki declaration,
and written informed consent was obtained from all participants.
The study was approved by our Institutional Ethics Committee
(ethical approval no: 22-02-12/20).
Patient characteristics
Eighty-nine women with ovarian masses were enrolled in the
study: 56 women with an ovarian endometrioma (endometrioma
group) and 33 women with a benign ovarian cyst (control group).
Age, parity, body mass index, tobacco use, alcohol use, diameter of
the ovarian mass, bilaterality of the mass, platelet count, neutrophil
leukocyte ratio, serum follistatin, serum CA-125, and serum CA 199 levels were determined for each participant.
All patients in the endometrioma group had Stage 3 or 4
endometriosis according to the revised American Society for
Reproductive Medicine classification [12]. Patients in the control
group did not have endometriosis but had benign ovarian tumors
with histological confirmed final diagnoses, including serous
(n ¼ 18) and mucinous (n ¼ 15) cystadenomas.
Blood samples
Peripheral venous blood samples were collected from all patients prior to laparoscopic cystectomy to measure serum follistatin, CA-125, and CA 19-9 levels. All blood samples were allowed
to clot at room temperature. Samples were centrifuged at 300g for
20 minutes at room temperature, and the serum was separated
using a disposable pipette, transferred to a cryoresistant tube, and
stored at À80 C for 3e15 months (average 9 months).
Laboratory assays

The serum follistatin concentration was measured using a
commercially available enzyme-linked immunosorbent assay
(ELISA; Eastbiopharm Co., Ltd., Hangzhou, China). For the follistatin
ELISA, the intra- and inter-assay coefficients of variation were 3%
and 9%, respectively.
The serum concentration of CA-125 was measured using an
electrochemiluminescence immunoassay kit (Roche Elecsys Kits,
Roche Diagnostics, Mannheim, Germany). The intra- and interassay coefficients of variation were 3.8% and 1.5%, respectively.
The reference range for serum CA-125 was 0e35 IU/mL.
Serum CA 19-9 was measured using an electrochemiluminescence immunoassay (Roche Diagnostics E 170
analyzer). A normal CA 19-9 value was defined as < 27 IU/mL.

237

Results
Patient demographic and clinical features are presented in
Table 1. The mean age, parity, body mass index, tobacco use, and
alcohol use were similar between the endometrioma and the
control groups. There were no statistically significant differences
between the groups in terms of the mean platelet count or NLR
(p > 0.05). The mean diameter of the cystic mass was 6.79 ± 1.56 cm
in the control group (benign ovarian cyst) and 5.64 ± 2.01 cm in the
endometrioma group (p < 0.05). Serum CA-125, CA 19-9, and follistatin levels in the endometrioma group versus the control group
were 93.45 ± 89.55 IU/mL versus 47.25 ± 72.05 IU/mL,
84.79 ± 93.37 IU/mL versus 34.89 ± 76.9 IU/mL, and 9350 ± 895 pg/
mL versus 725 ± 72 pg/mL, respectively.
According to ROC curve analysis, the cut-off values (sensitivity
and specificity) for serum CA-125, CA 19-9, and follistatin were
23.2 IU/mL (81.14% and 72.73%), 30.14 IU/mL (45.28% and 87.5%),
and 23.5 ng/mL (53.57% and 60.61%), respectively (Fig. 1). The area

under the curve values for CA-125, CA 19-9, and follistatin were
0.814, 0.613, and 0.54, respectively (Table 2). Combining CA-125, CA
19-9, and follistatin levels using the cut-off values in Table 2
significantly improved the diagnostic accuracy with a specificity
of 93.75% and a sensitivity of 26.8%.
Table 1
The demographic and clinical characteristics of the patients.

Age (y)a
Parityb
BMI (kg/cm2)a
Smokersc
Alcohol usec
Bilateralityc
Diameter of the mass (cm)a
NLRa
CA-125 (IU/mL)a
CA19-9 (IU/mL)a
Follistatin (pg/mL)a

Endometrioma
group (n ¼ 56)

Benign cyst
group (n ¼ 33)

p

31.71 ± 7.79
0.70 (0e3)

2.77 ± 3.71
18 (32.14)
2 (3.5)
15 (28.57)
5.64 ± 2.01
2.36 ± 2.21
93.45 ± 89.55
84.79 ± 93.37
9350 ± 895

29.06 ± 10.75
1.06 (0e4)
2.3 ± 3.53
12 (36.36)
1 (3.03)
9 (27.27)
6.79 ± 1.56
2.39 ± 1.86
47.25 ± 72.05
34.89 ± 76.9
725 ± 72

0.692
0.788
0.532
0.365
0.278
0.976
0.007
0.964

0.014
0.010
0.011

BMI ¼ body mass index; NLR ¼ neutrophil lymphocyte ratio.
A p value <0.05 was considered statistically significant.
a
Data are presented as mean ± SD.
b
Data are presented as median (minemax).
c
Data are presented as n (%).

Statistical analysis
The means and standard deviations were calculated for
continuous variables, and normal distribution was analyzed using
the KolmogoroveSmirnov test. The Chi-square (c2) test and Student t test were used to evaluate associations between the categorical and continuous variables. For non-normally distributed
categorical variables, the ManneWhitney U test was used.
Receiver operator characteristic (ROC) curve analysis was used to
establish the cut-off values for follistatin, CA-125, and CA 19-9.
The Youden index (sensitivity ỵ specicity 1) was also calculated, and the cut-off value with the maximum Youden index was
deemed the optimal cut-off value. A p value < 0.05 was considered statistically significant. Statistical analyses were conducted
using SPSS 17.0 software for Windows (SPSS Inc., Chicago, IL,
USA).

Fig. 1. ROC curve of CA-125, CA 19-9, and follistatin for the discrimination of endometrioma cases from benign cysts. AUC ¼ area under the curve; ROC ¼ receiver
operating characteristic.


€ Ant et al. / Taiwanese Journal of Obstetrics & Gynecology 54 (2015) 236e239

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238

Table 2
The cut-off values of tumor markers and follistatin levels in the detection of ovarian endometrioma.

CA-125 (IU/mL)
CA19-9 (IU/mL)
Follistatin (pg/mL)

Cut-off

Sensitivity

95% CI

Specicity

95 % CI

ỵLR

LR

23.2
30.14
2350

82.14

45.28
53.57

69.6e91.1
31.6e59.5
3970e6700

72.73
87.5
60.61

54.5e86.7
71e96.4
4210e7710

3.01
3.62
136

0.25
0.63
0.77

CI ẳ condence interval; LR ẳ likelihood ratio.

Discussion
In the present study, serum follistatin levels were measured in
women with ovarian endometriomas or benign ovarian cysts.
Serum CA-125, CA 19-9, and follistatin levels were significantly
different between the two groups. Although the cystic mass

diameter was significantly greater in the benign cyst control group,
serum CA-125, CA 19-9, and follistatin levels were higher in the
endometrioma group. ROC curve analysis indicated that CA-125, CA
19-9, and follistatin might be discriminative markers for ovarian
endometrioma. The sensitivity and specificity of serum follistatin
for the diagnosis of endometrioma were 53.57% and 60.61%,
respectively.
The diagnosis of endometriosis is currently dependent upon
postoperative histopathological examination, since a noninvasive
method for the diagnosis of endometriosis has yet to be validated.
Biomarkers such as CA-125, annexin V, vascular endothelial growth
factor, soluble intercellular adhesion molecule-1, and glycodelin
have been investigated as potential diagnostic markers for endometriosis [13]. However, despite advanced technological developments, an ideal diagnostic biomarker has not been identified.
In a meta-analysis, CA-125 was a better diagnostic marker for
Grades 3 and 4 endometriosis than Grades 1 and 2 endometriosis
[14]. In another study, serum CA-125 levels were similar between
women with Grades 1 or 2 endometriosis and those without
endometriosis. However, serum CA-125 levels were found to be
significantly higher in women with Grades 3 or 4 endometriosis
than Grade 1 endometriosis [15]. In the present study, all patients
in the endometrioma group had Grades 3 or 4 (severe) endometriosis, and when CA-125 levels were compared between the
endometrioma group and the control group, the predictive value of
CA-125 was significantly higher in the endometrioma group with
severe endometriosis.
The diagnostic significance of CA 19-9 levels in endometriosis
remains unclear due to conflicting data [16e18]. While one study
reported significantly higher CA 19-9 levels in all stages of endometriosis [16], others reported no association between serum CA
19-9 levels and endometriosis [17,18]. In the present study serum
Ca-19-9 levels were not significantly different between the endometrioma and control groups.
Follistatin was first isolated from follicular fluid [10], and 15

years after its initial isolation, it was detected in human endometrium [19]. Follistatin was first investigated as a potential biomarker
for endometriosis in 2009 by Florio et al [11].
During the late secretory phase of the menstrual cycle, Rocha
et al [20] found an increase in follistatin mRNA in the eutopic
endometrium and in endometriomas of women with endometriosis compared with healthy controls. Therefore, it has been suggested that activin and follistatin mRNA expression are altered in
endometriosis and can be used for diagnostic purposes [20]. In
another study, follistatin, follistatin-related gene, and activin A
binding proteins showed an impaired expression pattern in women
with endometriosis, which may cause insufficient angiogenesis and
endometrial differentiation due to altered activin A expression [7].
Altered follistatin expression and the subsequent physiologic
changes detailed above may account for the association between

high follistatin levels and infertility in women with endometriosis.
Additional research is needed to investigate this hypothesis.
In a study by Floria et al [11], serum follistatin levels were higher
in women with ovarian endometrioma than those with benign
ovarian cysts. In addition, the level of follistatin was significantly
higher in cystic fluid than in peritoneal fluid. Therefore, the authors
claim follistatin had high sensitivity and specificity for ovarian
endometrioma and was a useful diagnostic marker. However, this
finding is not consistent with data from the present study. Our data
indicate that while serum follistatin was significantly different
between the endometrioma and control groups, CA-125 is a superior diagnostic marker for the discrimination between ovarian
endometriomas and benign ovarian cysts. In a recent study of 28
biomarkers, the combined evaluation of serum annexin V, vascular
endothelial growth factor, CA-125, and soluble intercellular adhesion molecule-1 or glycodelin had a sensitivity of 81e90% and a
specificity of 63e81% for the diagnosis of endometriosis [13]. In the
present study, the combination of CA-125, CA 19-9, and follistatin
levels produced a high specificity of 93.75% and a low sensitivity of

26.8% for the diagnosis of endometriosis.
In summary, follistatin may be a promising marker for the
diagnosis of endometriosis, although CA-125 was determined to be a
superior diagnostic marker for severe (Stages 3 and 4) endometriosis
and ovarian endometrioma. There are limited studies on the association between follistatin levels and endometriosis in literature,
and this study provides important information about serum follistatin levels and endometriosis. However, additional investigations
using large study populations should be carried out to identify other
promising biomarkers for the diagnosis of endometriosis.
Conflicts of interest
The authors have no conflicts of interest relevant to this article.
Acknowledgments
We would like to thank www.textcheck.com (certificate/
aHQWcC) for the English revision of our manuscript.
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