L.I. Medved's Research Center of Preventive Toxicology, Food and Chemical Safety, Ministry of Health of Ukraine, Kyiv, Ukraine

Abstract. Introduction. The authors in previous studies have found a high level of exposure to manganese and nickel in women with polycystic ovary (PCOS).
Goal of research. The purpose of conducted research was to assess the pituitary-gonadal system in women with polycystic ovary during high level of exposure with manganese and nickel.
Material and methods. Studies were conducted for two groups of women. The first group — control consisted of healthy women of reproductive age. The second group consisted of women with PCOS. From study were excluded women with thyroid disease, diabetes, prolactinomas and other endocrine diseases.
Using ELISA, in the early follicular phase measured in serum luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol. All studies were performed with the consent of the patient and with compliance with ethical standards.
Statistical processing was carried out with the definition of arithmetic mean, median. The validity of the obtained results was evaluated using following indicators: Shapiro-Wilka test, Fisher's F-test, Mann-Whitney’s U-test.
Results. Studies have shown that in women with PCOS there is an increase in LH (p=0,0073). FSH and estradiol are not statistically different from the control group. Only in 23,33 % of cases the ratio of LH/FSH breached the ratio of 2:1. In women with PCOS, a large range of deviation of LH, FSH, and estradiol values from median values was recorded. Such changes can indicate pituitary-gonad system dysfunction. Possible mechanisms of negative effects of manganese and nickel on the pituitary gonad system are still under discussion.
Conclusion. The obtained results indicate dysfunction of the pituitary gonad system during high level of exposure with manganese and Nickel. In women with PCOS there are signs of dysfunction of the secretion of gonadotropins and estradiol. The use of LH/FSH for PCOS diagnostics is inappropriate.
Key words: pituitary, ovary, hormones, polycystic ovary syndrome, manganese, nickel.

The function of the ovaries is controlled by the pituitary-hypothalamic system through feedback. Normally, pulsatile secretion of gonadotropin-releasing hormone (GnRH) provides a rhythmic secretion of the luteinizing hormone (LH) and follicle-stimulating hormone (FSH). It is under their influence that follicle growth and maturation, ovulation, and yellow body functioning occur. The change in the frequency of GnRH secretion affects not only the amount of LH and FSH, but also the ratio of these hormones.

In polycystic ovaries (PCO), GnRH hypersecretion and increase in the frequency of GnRH impulse secretion are observed. Such changes are accompanied by the increased secretion of LH and LH/FSH ratio disorder. However, recently, the attitude towards the use of LH/FSH ratio as a diagnostic criterion of PCO is revised. In women with PCO, there is the ovary function disorder. Normally, LH stimulates the estrogen secretion in follicles with the size of 9–10 mm. In PCO, under the influence of LH, estrogen secretion begins earlier, in antral follicles of up to 4 mm in size. In addition, with the follicle size of 6–8 mm, the estradiol values are close to preovulatory ones. Such changes suppress FSH secretion and stop the further development of follicles. However, estradiol values in PCO are practically unchanged or have slight deviations [1].

Factors that may interfere with the gonadotropin secretion include the stress that causes the pituitary-hypothalamus system activation and changes the GnRH secretion. Similar effects may be caused by exogenous endocrine disruptors. In addition to disturbing the pituitary-hypothalamus system functioning, endocrine disruptors disturb folliculogenesis and steroidogenesis in the ovaries.

Our studies have shown that women with PCO have high blood serum levels of manganese and nickel [2].

The WHO attributed manganese to endocrine disruptors [3]. Nickel is a known metalloestrogen capable of disturbing the function of the pituitary gland and the ovaries [4].

Thus, we have reasons to suppose that manganese and nickel can be involved in the occurrence of PCO. In previous studies, we found that increased exposure to manganese and nickel is accompanied by signs of hormonal stress [5]. Thus, in this study, we consider the possible pathogenetic consequences of increased action of manganese and nickel on the function of the hypophysis-gonade system in women with PCO.

The objective of this work is to study the state of the hypophysis-gonade system in women with polycystic ovaries in conditions of increased exposure to manganese and nickel.

Materials and methods of the study. The study included 2 groups of women. The first group included women with PCO. The study did not include patients who were diagnosed with Cushing disease, thyroid gland pathology, prolactinoma. The second group was the control one and included healthy women of reproductive age. The analysis of the blood serum hormones were conducted in the early follicular phase using EIA methods: LH, FSH, estradiol. In certain cases, it was not appropriate or possible to determine all the above hormones. For this reason, the number of observations regarding certain hormones may be different. All examinations were performed with the consent of the patients and consistent with ethical standards.

Statistical processing was carried out using the Statistica software. The verification of the normality of distribution was carried out using the Shapiro – Wilk and Kolmogorov – Smirnov tests. Homogeneity of variance was checked using F-test. The validity of the results was evaluated using the Mann – Whitney U test.

Results and their discussion. According to the Rotterdam Consensus, almost 95 % of women with PCO have a increased ratio of LH/FSH. The issue of the diagnostic value of this indicator for the diagnosis of PCO has been discussed for a long time. However, the last European Society of Endocrinology discussed the inappropriateness of using the LH/FSH ratio for PCO diagnosis.

Our studies have shown that in women with PCO there is an increase in LH values compared to the control group. The FSH values in both groups did not differ significantly (see Table).

Table. LH, FSH and estradiol values in the control group and in polycystic ovaries

p — Mann – Whitney U test
n — number of observations
М — arithmetic mean value
SD — standard deviation
Med. — median

Despite the high LH values, in women with PCO, the LH/FSH ratio in most cases did not exceed 1:2. Only in 7 cases (23.33 %) this value was higher. Thus, our results proves the inappropriateness of using the LH/FSH ratio for PCO diagnosis.

We drew attention to the fact that, unlike the control group, there was a large range of deviations of LH and FSH values from median values in women with PCO (see Figures 1 and 2). In our opinion, such changes may be a manifestation of the pituitary-hypothalamus system dysfunction in women with PCO.

Fig. 1. LH values in the control group (1) and in polycystic ovaries (2).

Fig. 2. FSH values in the control group (1) and in polycystic ovaries (2).

Available literature data suggest that exposure to manganese and nickel can cause a disturbance of gonadotropic hypophysary function. Thus, the experiment showed that manganese causes the increased level of gonadotropins and estradiol [6]. Exposure to nickel also increases the gonadotropins secretion, but reduces the estradiol levels [4]. These effects are dose-dependent. Low doses of exposure cause the increased LH secretion, and higher doses does not cause LH increase. The manganese effects on the hypophysis are mediated through the hypothalamus, but not the hypophysis. Manganese is accumulated in the preoptic area and the mediobasal hypothalamus. It is shown that in this case, there is a blockade of GnRH receptors in the hypothalamus and an increase in the GnRH secretion [7].

We have not found works on the study of manganese and nickel effects on gonadotrophic hypophysary function in women. However, data regarding men show: Exposure to low doses of manganese is accompanied by an increase in LH levels [8]. The increase in LH and FSH values was observed in electroplaters exposed to nickel [9].

It would be logical to assume that an increase in the gonadotropin level causes an increase in the estradiol secretion. In addition, the experiment showed that manganese increases the estradiol levels [6]. However, as it can be seen from the table, estradiol levels did not differ significantly between the two groups of women in our studies.

We drew attention to the fact that, in addition to increase in LH levels in women with PCO, estradiol and gonadotropin values showed significant deviations from the median values (Fig. 3). Such deviations confirm our assumption of the hypophysis-gonade system dysfunction in women in conditions of increased exposure to manganese and nickel. As a rule, the hypophysis dysfunction is accompanied by the disturbances of the gonadotropin secretion rhythm. It is the gonadotropin secretion rhythm that is a prerequisite for normal folliculogenesis and the body supply with the required amount of estradiol.

Fig. 3. Estradiol values in the control group (1) and in polycystic ovaries (2).

Folliculogenesis disturbance in women with PCO is exacerbated by the toxic properties of nickel. It has been experimentally shown that nickel exhibits genotoxic properties in ovarian cells in vitro. As a result, degenerative processes of granulosa cells are observed, steroidogenesis and apoptosis are disrupted [10]. Exposure to nickel nanoparticles causes a decrease in estradiol values in exposed rats, and the effect is dose-dependent. It has been histologically shown that exposure to nickel nanoparticles causes disturbances in lymph and blood circulation in the ovaries, leukocyte infiltration, and inflammation. According to the authors, such changes can disrupt ovarian estrogen production [4].

In fact, the stimulating effect of manganese on the estradiol secretion is neutralized by degenerative processes in the ovaries caused by nickel. It can be assumed that as a result of the competitive effects of manganese and nickel on estradiol secretion, we did not observe any differences in the values of the control and experimental group.

Thus, our studies have shown that increased exposure to manganese and nickel can be the cause of the hypophysis-ovarian system dysfunction. The hypothalamo-hypophysis-gonade system dysfunction in women with PCO can be related to direct toxic effects on the structure of the hypothalamus and ovaries. In addition, the dysfunction processes may be intensified by hormonal stress caused by increased levels of exposure to manganese and nickel. As we have shown earlier, women with PCO have signs of hormonal stress, manifested as increased levels of adrenal androgens, cortisol, as well as hyperprolactinaemia [5].

Our researches have shown that there is an increase in LH values in women with PCO. FSH and estradiol values do not differ from those of the control group. However, unlike the control group, in women with PCO, a large range of deviation of LH, FSH, and estradiol values from median values was observed. Such changes may be indicative of the hypothalamo-hypophysis-gonade system dysfunction. According to our data, the use of LH/FSH value for PCO diagnostics is inappropriate.

REFERENCES

1. The polycystic ovary syndrome: a position statement from the European Society of Endocrinology / G. Conway, D. Dewailly, E. Diamanti-Kandarakis [et al.]//Eur. J. Endocrinol. – 2014. –V.171, No. 4. – P.1–29.

2. Study of the balance of essential macro- and microelements in women with polycystic ovaries / S. V. Hunkov, T. F. Tatarchuk, V. O. Vykhor[et al.] // Suchasni problemy toksykolohii, kharchovoi ta khimichnoi bezpeky. – 2015. – V.72, No. 4, – P.51 – 53.

3. The State-of-the-Science of Endocrine Disrupting Chemicals – 2012.WHO (World Health Organization) / A. Bergman, J.J. Heindel, S. Jobling [et al.] // UNEP: Geneva: UNEP/WHO. – 2013. – 260 p.

4. Nickel nanoparticles exposure and reproductive toxicity in healthy adult rats / L. Kong, M. Tang, T. Zhang [et al.] //Int. J. Mol. Sci. – 2014. – V.15, No. 11. – P. 21253-21269.

5. Hunkov S.V. Hyperandrogenism in polycystic ovaries associated with stress caused by exposure to manganese and nickel / S.V. Hunkov // Zaporozhskii mediztsinskii zhurnal. – 2017. – No. 4. – P.462–466.

6. Possible developmental early effects of endocrine disrupters on child health. –World Health Organization: Geneva, Switzerland. – 2012. – 83 p.

7. Costa L.G. Manganese in Health and Disease / L. G. Costa, M. Aschner// Royal Society of Chemistry, 2015 – 654 р.

8. Wang C. Effects of low level manganese exposure on the serum neuroendocrine hormones in the welders / C. Wang, J. P. Lu, Y. M. Jiang//Zhonghua Lao Dong Wei Sheng Zhi Ye Bing Za Zhi. – 2011. – V.29, No. 2. – P.94 – 97.

9. Beshir S. Hormonal Perturbations in Occupationally Exposed Nickel Workers/ S. Beshir, K. S. Ibrahim, W. Shaheen, E. M. Shahy //Open Access Maced. J. Med. Sci. – 2016. – V.4, No. 2. – P.307-3011.

10. Nickel-induced structural and functional alterations in porcine granulosa cells in vitro / J. Kročková, P. Massányi, A. V. Sirotkin [et al.] //Biol. Trace Elem. Res. -2013. – V.154, No. 2. – P.190 – 195.

Надійшла до редакції 31.10.17