Insulin-like growth factor-1 on cycle day 2 and assisted reproductive techniques outcome: A cross-sectional study

Abstract Background Individualized assisted reproductive techniques (ART) can improve ART outcomes. Some studies suggested using insulin-like growth factor-1 (IGF-1) level on cycle day 2 for individualized ART. Objective To investigate the relationship between serum levels of IGF-1 on day 2 of the cycle and ART outcomes. Materials and Methods In this cross-sectional study, cycle day 2 serum levels of IGF-1 were measured in 175 women aged between 18-44 yr as candidates for in vitro fertilization or intracytoplasmic sperm injection. All participants received antagonist protocol, and the relationship between serum levels of IGF-1 and ART outcomes according to the number of oocytes were investigated; poor responders (oocytes < 5), normal responders (oocytes 5-15), and hyper responders (oocytes > 15). Results Poor responders had higher serum level of IGF-1 when compared with normal and hyper-responders; however,this difference was not statistically significant (p = 0.41). The serum levels of IGF-1 in women with zero retrieved oocytes and those cycles that were canceled for the inappropriate ovarian response were not significantly different compared to other women in the group of poor responders. An inverse relationship was observed between the serum level of IGF-1 and anti-Mullerian hormone. Furthermore, no significant relationship between serum level of IGF-1 with age, body mass index, number of 2 pronucleus, and number of embryos was observed. Conclusion According to our results, the serum levels of IGF-1 may not be able to predict ART outcomes. It seems necessary to conduct more studies with larger sample size.


Introduction
10-15% of couples suffer from infertility. Many of these patients need assisted reproductive techniques (ART) (1). One of the suggestions to improve ART outcomes, especially in poor responders (5-35% of ART cycles) (2)(3)(4), is individualized ovarian stimulation (5, 6) that needs efficient and reliable indicators. An ideal dynamic indicator shows the effect of pretreatment and adjuvant therapy on the metabolic environment of oocytes and can improve ART outcomes (7).
Currently, indicators such as anti-Mullerian hormone (AMH), follicle-stimulating hormone (FSH), antral follicle count, and the dynamic tests of the ovarian reserve like clomiphene citrate challenge test, are used for individualized ovarian stimulation (8). The high cost and low efficiency of these indicators, especially their inability to show the effect of pretreatments on ART outcomes, lead to a search for more cost-effective indicators.
The insulin-like growth factor-1 (IGF-1) is one of the subjects that has the attention of researchers for its role in oocyte growth and embryo quality (9)(10)(11). IGF-1 is a single-chain polypeptide that is produced in the liver in response to growth hormone and transported to the organs, which mediates growth hormone effects (8). This factor can induce granulosa cell proliferation and on the other hand, FSH itself can facilitate granulosa cell synthesis of IGF-1 it regulates the entrance of follicles from the gonadotropin-independent stage to the gonadotropin-dependent stage. Also, IGF-1 stimulates folliclular growth and oocyte maturation by increasing the aromatase enzyme activity and the production of estrogen, progesterone, and the expression of the LH receptor (12)(13)(14)(15).

IGF-1 increases FSH actions in granulosa cells in
rodents and also low IGF levels in the follicular fluid lead to decreased response to FSH in in vitro fertilization (IVF). In addition, IGF-1 receptor inactivation has been associated with ovulatory dysfunction and infertility (17,18), and lower levels of IGF-1 in follicular fluid are associated with lowquality oocytes and embryos (19)(20)(21). Increasing IGF-1 in follicular fluid in women > 35 yr old leads to improved cycle outcomes (22). Studies have shown that level of IGF-1 on the day 2 of the menstrual cycle has an inverse relationship with the ovarian response. And the IGF-1 serum level was found to be significantly higher in poor responders compared to women with normal and hyper responses. Decreased IGF-1 levels after estradiol pretreatment at the end of the late follicular phase improves ART outcomes (7,23). Now the question arises is, can IGF-1 have a predictive value to individualize ovarian stimulation in ART cycles.
The present study was designed to investigate the relationship between serum levels of IGF-1 on the day 2 of cycle and ART outcomes.

Materials and Methods
This cross-sectional study was conducted at

Sample size
Considering the confidence level of 95%, the power of 80%, and the sensitivity of 70% for IGF-1 according to a similar study and the loss of 10%, the minimum required for sample size was detected.
The following formula was used:

Ethical considerations
The study was approved by the Ethics

Statistical analysis
The

Results
Initially, 188 women were eligible to enter the study. Of them, 13 women were excluded due to the lack of information. Finally, the data from 175 women were analyzed and compared in 3 groups, the poor responders (n = 63), the normal responders (n = 82), and the hyper responders (n = 30).
The age in the poor responders was significantly higher than the normal and hyper responders; however, no significant difference was observed between the hyper and normal responders. AMH was found to be significantly lower in the poor responder group (Table I (Table II).

Discussion
In this cross-sectional study, we investigated the relationship between the serum levels of IGF-1 on day 2 of the menstrual cycle and ART outcomes.
Our results showed that serum levels of IGF-1 in the poor responders were higher than normal and hyper-responders but no significant difference was observed.
A retrospective study on 167 women, showed that the serum level of IGF-1 in poor responders is higher than in normal and hyper responders. Also, they found IGF-1 levels more than 70 ng/mg, with a sensitivity of 85 and a specificity of 80%, associated with a negative pregnancy result (23).
Another retrospective study on 184 cycles, showed that the IGF-1 level on day 2 of the cycle was significantly higher in women with poor ovarian response than in normal and hyper responders.
Pretreatment with estradiol in the luteal phase decreased the serum level of IGF-1 and increased the number of retrieved oocytes and cumulative pregnancy rate. However, no effect on oocyte maturation rate and fertilization rate was seen.
Also, they reported higher IGF-1 levels in women with canceled cycles where they concluded that an IGF-1 level of more than 72 ng/mg is a strong negative indicator for ART outcomes. By a receiver operating characteristic curve with 70% sensitivity and 78% specificity in poor responders, they suggested an IGF-1 level of more than 72 ng/mg as a threshold for delaying cycle until reducing the IGF-1 level with estradiol pretreatment (7).
Follicular resistance to IGF-1 can lead to an increased level of IGF-1 in poor responders (7).
Ligand-dependent internalization of receptor has been suggested as the cause of resistance to IGF-1 (24). The present study showed an inverse relationship between the serum IGF-1 levels on day 2 of the cycle and AMH. While the level of IGF-1 was not related to BMI and age.
Yovich et al. reported no correlation between IGF profiles in the early follicular phase and AMH and antral follicle count (25). Another study reported an inverse relationship between age and serum level of IGF-1 (26). Considering the function of IGF-1 as a biochemical marker of follicular function, the use of IGF-I in follicular fluid as a potential marker of embryo quality and predictor of ART outcome was investigated (6,21,22). Some studies showed that the level of IGF-1 in the follicular fluid is directly related to the embryo quality and the pregnancy rate (6,21,22).
In women over 35 yr, the chance of pregnancy increases with the increase of IGF-1 in the follicular fluid. Treatment of poor ovarian responders is one of the most challenging topics in infertility.
Using different ovarian stimulation protocols and increasing the dose and duration of stimulation with gonadotropins, in these patients, did not significantly improve ART outcomes (27,28). Some research showed that increasing IGF-1 with growth hormone administration effectively improves ART outcomes in poor responders. Studies are being conducted to examine the possibility of prescribing growth hormones based on the serum level of IGF-1 (7,19,29,30).
Reducing serum level of IGF-1 in poor responders by estradiol pretreatment has improved ART outcomes (7). In another way some researchers reported that pretreatment with estradiol in women with poor ovarian response did not increase the number of retrieved oocytes and fertilization rate (31). Finally, considering the conflicting results on the relationship between serum levels of IGF-1 with age, AMH level, and ART outcomes, it seems necessary to conduct more studies in this field.

Conclusion
According to our results, cycle day 2 serum levels of IGF-1 in the poor responder group were higher than the normal and the hyper responders; however, this difference was not statistically significant. The serum level of IGF-1 may not be able to predict ART outcomes. It seems necessary to conduct more studies.