GYNECOLOGIC ENDOCRINOLOGY AND REPRODUCTIVE MEDICINE

Assessment of ovarian stromal blood flow after metformintreatment in women with polycystic ovary syndrome

Ahmed K. Makled • Mohamed El Sherbiny •

Rania Elkabarity

Received: 23 July 2013 / Accepted: 9 October 2013

� Springer-Verlag Berlin Heidelberg 2013

Abstract

Purpose To authenticate the effect of metformin treat-

ment on ovarian stromal blood flow in women with poly-

cystic ovary syndrome (PCOS) using 3-dimensional (3D)

power Doppler.

Methods The current case–control study was conducted

at Ain Shams University Maternity Hospital. A total of 60

women diagnosed to have PCOS were included as group 1.

Another 40 fertile women who were recruited from out-

patient clinic for contraception without PCOS with regular

menstrual cycles were included as control group (group 2).

All women underwent 3D power Doppler evaluations of

ovarian stroma. Anthropometric, hormonal and biochemi-

cal criteria were also measured. All women in group 1

received metformin hydrochloride 500 mg tablets, which

were started in a step-up maneuver every 5 days, from one

to three tablets per day. The same parameters were also

measured after the 3 months duration of treatment.

Results A total of 100 women were finally analyzed. At

the start of the study, there were no statistically significant

differences between group 1 and group 2 and regarding age

and body mass index, but the waist/hip ratio and Ferriman–

Gallwey scoring were statistically different between the 2

groups. The mean ovarian volume and stromal volume

were significantly larger in group 1. 3D power Doppler

indices [the vascularization index (VI), the flow index (FI)

and the (VFI) vascularization-flow index] were much

higher in group 1 than in group 2 (1.38 ± 0.76 vs.

4.69 ± 1.37, P \ 0.05, 26.59 ± 2.26 vs. 32.66 ± 4.37,

P \ 0.05, and 0.76 ± 0.39 vs. 1.54 ± 0.69, P \ 0.05,

respectively). After 3 months of using metformin in normal

weight PCO women, there was a statistically significant

improvement in group 1 regarding, hirsutism, most of

hormonal measurements. Also 3 months metformin treat-

ment significantly reduce VI, FI and VFI (4.69 ± 1.37 vs.

2.95 ± 1.52, P \ 0.05, 32.66 ± 4.37 vs. 29.48 ± 4.98,

P \ 0.05 and 1.54 ± 0.69 vs. 1.21 ± 0.7 P \ 0.05,

respectively). Using Receiver operator characteristic, there

was no cut-off value of VI, FI or VFI to detect ovulation in

women of PCOS.

Conclusions Metformin seems to have a beneficial effect

in normal weight PCO women via correcting ovarian

stromal blood flow and hormonal profiles.

Keywords Metformin �Ovarian stromal blood flow �Polycystic ovary syndrome � 3D power Doppler

Abbreviations

CI Confidence interval

3D 3-dimensional

ASRM American Society for Reproductive Medicine

BMI Body mass index

ESHRE European Society for Human Reproductive and

Embryology

ICC Intraclass correlation coefficient

FI Flow index

All authors have contributed significantly and are responsible about

the content of this manuscript.

A. K. Makled (&)

Department of Obstetrics and Gynecology, Faculty of Medicine,

Ain Shams University, Abbasia, Cairo, Egypt

e-mail: drahmedmakled@live.com

M. El Sherbiny

Ultrasound and fetal care unit, Ain-Shams University,

Cairo, Egypt

R. Elkabarity

Department of clinical pathology, Faculty of Medicine,

Ain-Shams University, Cairo, Egypt

123

Arch Gynecol Obstet

DOI 10.1007/s00404-013-3057-8

FSH Follicle-stimulating hormone

HCG Human chorionic gonadotropin

HDL High density lipoprotein

HOMA Homeostatic model assessment

LDL Low density lipoprotein

LH Luteinizing hormone

PCOS Polycystic ovary syndrome

PRF Pulse repetition frequency

QUICKI Quantitative insulin sensitivity check indexes

ROC Receiver operator characteristic

SD Standard deviation

STIC Spatiotemporal image correlation

TG Triglycerides

TVUS Transvaginal ultrasound

VFI Vascularization-flow index

VI Vascularization index

WHR Waist-to-hip ratio

Introduction

The Polycystic ovary syndrome (PCOS) is a heterogeneous

disorder, whose principal features include androgen excess,

insulin resistance, ovulatory dysfunction, and/or polycystic

ovaries, and is recognized as one of the most common

endocrine/metabolic disorders of women [1]. PCOS

accounts for 10–15 % of female infertility and about 80 %

of anovular infertility, in particular [2]. Currently, there is

increasing evidence that insulin sensitizers are particularly

effective in inducing ovulation in patients with PCOS [3].

Metformin, a biguanide, is the most widely used drug for

the treatment of type 2 diabetes worldwide. Its primary

action is to inhibit hepatic glucose production, but it also

increases the sensitivity of peripheral tissues to insulin. The

increase in insulin sensitivity, which contributes to the

efficacy of metformin in the treatment of diabetes, has also

been shown in non-diabetic women with the PCOS [4]. In

women with PCOS, long-term treatment with metformin

may increase ovulation, improve menstrual cyclicity, and

reduce serum androgen levels [5]; the use of metformin

may also improve hirsutism [6]. Ovarian stromal blood

flow dysfunction has been authenticated by different ways

in women with PCOS. Insulin action and nitric oxide

production may authenticate the link between endothelial

dysfunction and insulin resistance. The mechanism of this

resistance may be due to post-binding defect in insulin

receptor-mediated intracellular signaling ideology [7].

Defective endothelial vasomotor function in PCO women

resulting in anatomical and functional vessel changes

which can be detected by Doppler US and can be improved

by metformin treatment [8, 9]. 3-dimensional (3D) power

Doppler ultrasound is a beneficial non-invasive method to

authenticate the vascularization of the ovarian stroma in

women with PCO [10]. 3D Doppler ultrasound is pro-

gressively used in authenticating ovarian stromal blood

flow and has displayed lower impedance to flow in ovarian

stromal vessels in PCOS women [11]. The aim of the

current work was to authenticate the effect of metformin

treatment on ovarian stromal blood flow in women with

PCOS using 3D power Doppler.

Patients and methods

This case–control study was conducted at Ain Shams

University Maternity Hospital during the period from

September 2012 to June 2013 after being approved by the

ethical and research committee of council of Obstetrics and

Gynecology Department, Ain Shams University. The study

purpose and procedures were explained to all enrolled

women and a written informed consent was obtained from

each participant. The included women were divided into 2

groups: group 1 (cases) 60 women who were recruited from

patients attending infertility outpatient clinic with a diag-

nosis of PCOS and group 2 (controls) 40 fertile women

who were recruited from outpatient clinic for contraception

without PCOS with regular menstrual cycles. PCOS was

diagnosed according to criteria stated by European Society

of Human Reproduction and Embryology (ESHRE) and

American Society of Reproductive Medicine (ASRM) by at

least 2 out of 3 of the following: menstrual disturbance

(amenorrhea or oligomenorrhea), clinical and/or biochem-

ical sign of hyperandrogenism and/or typical ultrasono-

graphic finding of PCO (with one ovary being sufficient for

diagnosis), defined as the presence of 12 or more follicles

measuring 2–9 mm in diameter or ovarian volume over

10 ml [12]. Women with hyperandrogenism for causes

other than PCOS (e.g., congenital adrenal hyperplasia,

presence of androgen secreting tumors or Cushing syn-

drome), diabetic women, women receiving any drugs

which affect carbohydrate metabolism within 3 months

before the study, women with hyperprolactinemia or thy-

roid disorders, were excluded. None of the included women

received medical treatment for induction of ovulation for

the preceding 3 months. Before starting treatment, venous

blood samples were taken from all women on day 3 of

spontaneous menses or withdrawal bleeding after 5-day

treatment of oral norethisterone 10 mg daily, after fasting

for 8 h. The serum was divided into two samples. The first

sample was sent immediately for checking fasting blood

glucose. The other sample was stored at -20 �C till the

time of assay of all samples for serum insulin and free

testosterone, luteinizing hormone (LH), follicular stimu-

lating hormone (FSH) using immulite 2000 chemilumi-

nescent immunometric assay apparatus (Immulite,

Diagnostic Products Corp., Los Angeles, CA, USA). Mid-

Arch Gynecol Obstet

123

luteal progesterone was assayed using immulite 2000

chemiluminescent immunometric assay apparatus (Immu-

lite, Diagnostic Products Corp., Los Angeles, CA, USA).

Lipid profile [triglycerides (TG), Low density lipoprotein

(LDL) and high density lipoprotein (HDL)] was assayed

using synchron autoanalyser (Beckman instrument incor-

poration, California, USA). Blood samples were taken at

the end of the treatment period for re-checking serum

levels of previously measured parameters. Anthropometric

measurements were assessed before and three months after

treatment, these included, body mass index (BMI) waist-to-

hip ratio (WHR). BMI was calculated through the formula

BMI ¼ weight kilograms½ �=height2 m2½ �� �

. WHR was

defined as the ratio between the smallest circumference of

torso (between the 12th rib and iliac crest) and circum-

ference of the hip (which is the maximal extension of the

buttocks) [13]. Homeostatic model assessment (HOMA)

and the quantitative insulin sensitivity check indexes

(QUICKI) were used for assessment of insulin resistance.

HOMA was calculated as: ½fasting plasma

glucose mmol/lð Þ � fasting plasma insulin IU/mlð Þ�=22:50.

QUICKI was calculated as: 1=½log INSULIN;ðlIU/mlÞ � log GLUCOSE; mg/dlð Þ�. Mid-luteal serum

progesterone was also measured. Assessment of hirsutism

was done by Ferriman–Gallwey (FG) score C8 indicated

hirsutism [7]. All women had Transvaginal ultrasound

(TVUS) using transvaginal 3D power Doppler Voluson� E6

systems (Voluson Expert, General Electric Medical Sys-

tems, Milwaukee, WI), with a 4–9 MHz curved transducer.

The examinations were done during the early follicular

phase (days 4–7). All TVUS examinations were done by a

single senior observer who was blind to allocation. Total

follicular volume, total ovarian volume, stromal volume, the

vascularization index (VI), the flow index (FI) and the (VFI)

vascularization-flow index were measured as previously

described by Battaglia et al. By subtracting the total follic-

ular volume from the total ovarian volume we calculated the

stromal volume [11]. All patients were examined under the

same conditions. For every woman the power Doppler set-

ting was standardized as follows: gain, 4.20; frequency, mid;

Quality, high; wall motion filter, low 2; pulse repetition

frequency (PRF), 1.30 kHz; gray map, 6; balance, 205;

threshold, 30; ensemble, 23. The sampling volume angle

was set to 50. All women in group 1 received metformin

hydrochloride 500 mg tablets (Glucophage�, Bristol-Myers

Squibb, New York, USA) that was started in a step-up

maneuver every 5 days, from one to three tablets per day.

This dose was guarded as tolerated throughout the 3 months

of the study. TVUS was also performed every other day

starting from day 9 of the first spontaneous or induced cycle

following the 3 months treatment period. TVUS was per-

formed; good response was achieved when at least one

mature follicle becomes C18 mm in diameter. When the

optimal follicle size was reached, human chorionic gona-

dotropin (HCG) [10,000 IU] (Choriomon�, [5,000 IU]

IBSA, Switzerland) was given intramuscularly. Women

were reassessed by TVS, 48 h after administration of HCG

for ovulation signs (free fluid in the pouch of Douglas and/or

transformation of the mature follicle into corpus luteum)

[14]. Quantitative bhCG was done 2 weeks later to confirm

chemical pregnancy. TVS was performed 4 weeks after

positive bhCG to confirm the presence of intrauterine

pregnancy. The women were advised not to take any other

drugs or do any modifications in their life style (i.e., losing

weight, herbal products etc.).

Sample size justification

The sample size was determined to produce study power of

80 % and the statistical significance is set to 95 %, based

on the ovarian stromal VI differences between PCOS

women and controls reported by Pan et al. [15]

(3.99 % ± 2.38 vs. 1.44 % ± 1.20).

Statistical analysis

The statistical analysis was performed using the SPSS soft-

ware (19.0 version, SPSS Inc., Chicago, IL, USA). The

description of quantitative (numerical) variables was per-

formed in the form of mean ± standard deviation (SD). The

description of qualitative (categorical) data was performed in

the form of number of cases and percentage. The analysis of

numerical variables was performed using independent Stu-

dent’s t test or paired t test in the same group. The Pearson

correlation coefficient test was used to rank variables against

each other either positively or inversely. The mean differ-

ences of the differences between measurements of the same

observer were used as indicators of intraobserver repeat-

ability. A best intraobserver repeatability was achieved when

the mean of the differences was very close to 0. The Intra-

class correlation coefficient (ICC) and 95 % confidence

interval (CI) were used as expressions of reliability. They

vary from 0 to 1, which indicates the maximum reliability.

Values greater than 0.70 are usually accepted as good cor-

relation coefficients [16]. Receiver–operating characteristics

(ROC) curves were done for the 3 indices (VI, FI and VFI)

and we tried to define a cut-off value to predict improvement

in ovarian function by 3D Doppler indices.

Results

A total 100 women were finally analyzed. Comparison

between group 2 and group 1 at the start of the study

Arch Gynecol Obstet

123

Table 1 Comparison between

group 2 and group 1 at the start

of the study regarding

demographic, anthropometric,

laboratory and radiological data

Data are presented as

mean ± standard deviation� Analysis using independent

t test

* Significant

Group 2

(n = 40)

Group 1

(n = 60)

P-value�

Age (years) 25.26 ± 2.22 25.46 ± 2.1 0.58

BMI (kg/m2) 30.71 ± 4.42 31.2 ± 4.75 0.549

The waist: hip ratio 0.62 ± 0.13 0.76 ± 0.17 \0.05*

Ferriman–Gallwey scoring 2.20 ± 1.5 8.51 ± 3.4 \0.05*

Low density lipoprotein (LDL) (mg/dl) 68.69 ± 12.35 104.18 ± 20.67 \0.05*

High density lipoprotein HDL (mg/dl) 46.23 ± 10.52 40.47 ± 13.82 \0.05*

Triglycerides (mg/dl) 145.71 ± 14.74 192.63 ± 27.51 \0.05*

Day 3 Luteinizing hormone (LH) mIU/ml 6.86 ± 1.8 10.68 ± 2.68 \0.05*

Day 3 follicular stimulating hormone (FSH) mIU/ml 9.53 ± 2 8.72 ± 2.52 0.088

LH/FSH ratio (day 3) 0.74 ± 0.24 1.26 ± 0.27 \0.05*

Free testosterone, ng/ml 0.66 ± 0.2 0.96 ± 0.26 \0.05*

Fasting blood glucose mg/dl 72.1 ± 6.61 106.18 ± 27 \0.05*

Fasting insulin uU/ml 3.83 ± 0.93 9.28 ± 2.03 \0.05*

Homeostatic model assessment (HOMA) 0.66 ± 0.21 2.42 ± 1 \0.05*

Quantitative insulin sensitivity check indexes (QUICKI) 0.41 ± 0.02 0.33 ± 0.02 \0.05*

Progesterone (day 21) 10 ± 1.82 1.45 ± 1.75 \0.05*

Mean ovarian volume (ml3) 4.30 ± 1.15 8.84 ± 1.67 \0.05*

Mean stromal ovarian volume (ml3) 3.52 ± 1.058 6.62 ± 1.6 \0.05*

Mean ovarian vascularization index (VI) % 1.38 ± 0.76 4.69 ± 1.37 \0.05*

Mean ovarian flow index (FI) (0–100) 26.59 ± 2.26 32.66 ± 4.37 \0.05*

Mean ovarian vascularization-flow index (VFI) (0–100) 0.76 ± 0.39 1.54 ± 0.69 \0.05*

Table 2 Comparison between

women of group 1 before and

after 3 months of metformin

treatment regarding

demographic, anthropometric,

laboratory and radiological data

Data are presented as

mean ± standard deviation� Analysis using Paired T test

* Significant

Before metformin

treatment

After metformin

treatment

P-value�

Body mass index (BMI) (kg/m2) 31.28 ± 4.75 30.27 ± 4.35 0.231

The waist: hip ratio 0.76 ± 0.17 0.74 ± 0.17 0.456

Ferriman–Gallwey scoring 8.51 ± 3.4 8.01 ± 3.4 \0.05* S

Low density lipoprotein (LDL) (mg/dl) 104.18 ± 20.67 96.22 ± 2.59 \0.05* S

High density lipoprotein (HDL) (mg/dl) 40.47 ± 13.82 42.64 ± 10.19 \0.05* S

Triglycerides (mg/dl) 192.63 ± 27.51 180.86 ± 27.9* \0.05* S

Day 3 Luteinizing hormone (LH) (mIU/ml) 10.68 ± 2.69 8.56 ± 2.9 \0.05*

LH/FSH (follicular stimulating hormone

ratio) (day 3)

1.26 ± 0.27 0.93 ± 0.36 \0.05*

Free testosterone, ng/ml 0.96 ± 0.26 0.79 ± 0.24 \0.05*

Progesterone (day 21) 1.45 ± 1.75 4.89 ± 3.97 \0.05*

Fasting blood glucose (mg/dl) 106.19 ± 27.03 78.22 ± 19.29 \0.05*

Fasting insulin (uU/ml) 9.28 ± 2.03 7.97 ± 2.27 \0.05*

Homeostatic model assessment (HOMA) 2.41 ± 1 1.53 ± 0.79 \0.05*

Quantitative insulin sensitivity check indexes

(QUICKI)

0.34 ± 0.02 0.36 ± 0.02 \0.05*

Mean ovarian volume (ml3) 8.84 ± 1.67 7.56 ± 1.48 \0.05*

Mean stromal ovarian volume (ml3) 6.62 ± 1.6 5.32 ± 1.46 \0.05*

Mean ovarian vascularization index (VI) % 4.69 ± 1.37 2.95 ± 1.52 \0.05*

Mean ovarian flow index (FI) (0–100) 32.66 ± 4.37 29.48 ± 4.98 \0.05*

Mean ovarian vascularization-flow index

(VFI) (0–100)

1.54 ± 0.69 1.21 ± 0.7 \0.05*

Arch Gynecol Obstet

123

regarding demographic, anthropometric, laboratory and

radiological data are shown in Table 1. Effects of

3 months of treatment with metformin in group 1 on

demographic, anthropometric, laboratory and radiological

data are shown in Table 2. The ICC with 95 % CI for 3D

power Doppler indices (VI, FI and VFI) and ovarian

volume were 0.95 (95 % CI 0.86–0.97), 0.95 (95 % CI

0.86–0.94), 0.96 (95 % CI 0.88–0.96), and 0.98 (95 % CI

0.96–0.98) respectively. The current study showed a sta-

tistically significant correlations between 3D power

Doppler indices of ovarian stroma and HOMA, WHR and

BMI (except VFI and BMI where the correlation was not

statistically significant). There was a negative correlation

between QUIKI and all 3D Doppler indices (Table 3). On

comparing women with normal weight [BMI \ 30 (kg/

m2) and Obese women [BMI C 30 (kg/m2)] after met-

formin in group 1, we found that there was a statistically

significant difference in fasting blood glucose. Although

fasting insulin difference was not statistically significant,

but the HOMA and QUIKI were significantly better in

normal weight women. Ovarian stromal 3D power

Doppler indices were better in normal weight women

except mean ovarian VFI, which was lower in normal

weight women, but it did not reach a statistically signif-

icant difference (Table 4). Although we detected ovula-

tion in 12 cases after using Metformin for 3 months in

women of group 1. Yet, pregnancy was not achieved in

any case. We did ROC curve analysis to get a cut-off

value to detect ovulation in PCO cases after using met-

formin for 3 months; nevertheless, there was no cut-off

value of VI, FI or VFI to detect ovulation in our study

(Fig. 1). Figure 2 shows ovarian volume by 3D power

Doppler before treatment. Figure 3 shows ovarian vascu-

latures by 3D power Doppler after treatment. Figure 4

shows VI, FI and VFI of ovarian stroma by 3D power

Doppler before treatment. Figure 5 shows VI, FI and VFI

of ovarian stroma by 3D power Doppler after treatment.

Discussion

To the best of our knowledge, the current study is the

largest study authenticating the effect of metformin treat-

ment on ovarian stromal blood flow using 3D power

Doppler ultrasound. The current study demonstrated that

3D power Doppler indices of the ovarian stroma were

significantly higher in women with PCOS, this agrees with

other investigators [17]. In our study, the 3D sonographic

parameters were significantly correlated with free testos-

terone as well as the Ferriman–Gallwey score. In addition,

hypertrophy of the stroma was correlated with increased

stromal blood flow. These findings may be explained by a

Table 3 Correlations between 3 dimensional power Doppler indices and some variables in group 1 after metformin treatment

HOMA QUICKI BMI (kg/m2) The waist: hip ratio

Mean ovarian vascularization index (VI) % r 0.364 -0.421 0.394 0.502

P-value \0.05* \0.05* \0.05* \0.05*

Mean ovarian flow index (FI) (0–100) r 0.375 -0.427 0.463 0.647

P-value \0.05* \0.05* \0.05* \0.05*

Mean ovarian vascularization-flow index (VFI) (0–100) r 0.473 -0.486 0.217 0.356

P-value \0.05* \0.05* 0.102 \0.05*

Analysis using Pearson correlation

HOMA Homeostatic model assessment, QUICKI Quantitative insulin sensitivity check indexes, BMI Body mass index

* Significant

Table 4 Comparison between normal weight and obese women with

PCOS (in group 1) after 3 months of metformin treatment

BMI \ 30

(kg/m2)

n = 31

BMI C 30

(kg/m2)

n = 29

P-

value�

Fasting blood glucose

(mg/dl)

72.13 ± 6.57 84.31 ± 25.24 \0.05*

Fasting insulin (uU/ml) 7.44 ± 1.97 8.50 ± 2.46 0.077

HOMA 1.23 ± 0.47 1.83 ± 0.95 \0.05*

QUIKI 0.37 ± 0.02 0.36 ± 0.02 \0.05*

Mean ovarian

vascularization index

(VI) %

2.48 ± 0.89 3.46 ± 1.87 \0.05*

Mean ovarian flow index

(FI) (0-100)

28 ± 4.38 31 ± 5.21 \0.05*

Mean ovarian

vascularization-flow

index (VFI)

1.13 ± 0.5 1.30 ± 0.88 0.373

BMI Body mass index, PCOS Polycystic ovary syndrome, HOMA

Homeostatic model assessment, QUICKI Quantitative insulin sensi-

tivity check indexes� Analysis using independent T test

* Significant

Arch Gynecol Obstet

123

mechanism of neovascularization or activation of vasoac-

tive factors that in turn may affect androgen synthesis

within the ovary [7]. Our results confirmed that the previ-

ous studies concluded that patients with PCOS have an

increased stromal volume and vascularity as evident by 3D

Doppler indices of ovarian stromal vasculature. Moreover,

Stromal vascularity is significantly higher in patients with

PCOS who are hirsute [18]. In group 1, the Doppler indices

(VI, FI and VFI) were improved in PCO women with

normal BMI after metformin treatment. This agrees with a

previous study which concluded that Pre-treatment with

metformin prior to intracytoplasmic sperm injection in

women with PCOS does not enhance clinical outcome.

Nevertheless, among normal weight PCOS women, preg-

nancy rates were improved in women pre-treated with

metformin [19]. The better response in normal weight PCO

women to metformin is authenticated by the hypothesis

that, in obese but not normal weight women, microvascular

and metabolic insulin sensitivity are decreased, indepen-

dent of PCOS. Therefore, obese PCOS women in particular

may be at increased risk of metabolic and cardiovascular

diseases [20]. Nevertheless, the results of our study were in

contrast to those of other investigators who concluded that

those patients with PCOS have an increased stromal vol-

ume and vascularity as evident by 3D Doppler indices of

ovarian stromal vasculature who are of normal weight [18].

A recent study in UK showed that low-dose therapeutic

Fig. 1 ROC curve analysis to get a cut off value to detect ovulation

in PCO cases after using metformin for 3 months. FI Flow index,

ROC Receiver operator characteristic, VI Vascularization index, VFI

vascularization-flow index

Fig. 2 Ovarian volume by 3D

power Doppler before treatment

with metformin

Arch Gynecol Obstet

123

regimen with rosiglitazone and Metformin (500 mg twice

daily), has commensurate useful impacts on metabolic,

hormonal and morphological criteria of PCOS, but no

manifest effect on vascular parameters in a population. The

previous study did not use 3D Doppler, also the differences

from our study may be attributed to the lower dose of

Metformin and the smaller sample size they used [21]. This

beneficial effect of metformin in improving the ovarian

stromal blood flow did not reflect on ovulation rate in 12

out of 60 (20 %) and no pregnancy occurred. This may be

attributed to the use of metformin only without concomi-

tant use of ovulation induction drugs. In the current study,

Fig. 3 Ovarian vasculatures by

3D power Doppler after

treatment with metformin

Fig. 4 VI, FI and VFI of

ovarian stroma by 3D power

Doppler before treatment with

metformin

Arch Gynecol Obstet

123

the power Doppler settings were standardized for all

women. Regarding the issue of standardization, the hope

will go some way towards standardizing machine settings

when evaluating 3D power Doppler indices. However,

even with such standardization, several feebleness of the

3D power Doppler technique will remain. For example,

there are differences in the approach in which tissues and

organs are evaluated [22]. Also, the effect of attenuation

should not be ignored, and can be avoided by normalizing

the intensity of signals during 2D assessment [23, 24].

Another manner to compensate for the effect of attenuation

and machine settings would be to settle indices that relate

maximum, average and minimum VI, FI and VFI noticed

during a cardiac cycle. However, this is only applicable if

the 3D power Doppler dataset is captured using spatio-

temporal image correlation (STIC). Without standardiza-

tion of all these issues, it is anticipated that investigators

will continue to obtain divergent results when assessing the

same end-point using 3D power Doppler [22, 25]. While it

is impractical to expect a consensus on all these parameters

in a short period of time, investigator believes that stan-

dardized machine settings would be a large step in the

appropriate direction [22].

The strength of the current study is that it is the largest

study authenticating the effect of metformin treatment on

ovarian stromal blood flow using 3D power Doppler

ultrasound. The limitations of the current study included

the non-inclusion of another control group with PCOS,

without treatment with metformin, but this may be due to

ethical point of view. Another limitation was the absence

of ovulation induction drugs, so as to increase the ovulation

rate and pregnancy rate, but we did not add these drugs so

as to assign the change in ovarian stromal blood flow to

metformin only and also some investigators considered that

metformin was one of ovulation induction drugs [5].

Lastly, another limitation is the failure of the ROC curves

to make a definitive cut-off value of VI, FI or VFI to detect

ovulation in women with PCOS.

Conclusion

Metformin seems to have a beneficial effect in normal

weight PCO women via correcting ovarian stromal blood

flow and hormonal profiles.

Conflict of interest The authors do not have any conflicts of

interest. All authors have substantially contributed to the concept and

design, acquisition of data, analysis and interpretation of data,

drafting the article and critical revision, and final approval of the

version to be published. The authors funded the research.

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