Infertility is an important worldwide reproductive disorder, and some couples are being affected every day as the population increases. Infertility problems affect various aspects of human beings. The prevalence of infertility varies from country to country ranging from less than 5% to over 30% (1,2). In Nigeria, it has been extrapolated that about 3–4 million couples have infertility problems, affecting 10%–30% of couples (3,4). Infertility is defined as a disorder of the reproductive system and the inability to become clinically pregnant after 1 year or more of regular unprotected sexual intercourse (5). Primary infertility is when a woman is unable to give birth to a child, either due to the failure to become pregnant or due to the failure to carry a pregnancy to term (6). Secondary infertility, on the other hand, is the inability to conceive for 1 year or more (2 years in some epidemiological studies) after having conceived at least once before (7). Causes of female infertility are many: including acquired or genetic causes, inability to ovulate, and malformation of the eggs (Figure 1). These causes could be due to deficiencies of 1 or more micronutrients or nutritional disorders that play significant roles in reproduction and may complicate conception (8). Smoking, alcoholism, and obesity are some of the risk factors capable of affecting fertility (Figure 2). Moreover, exposure to pollutants in the environment and some toxic substances directly can become toxic to human gametes (eggs and sperm), resulting in both decreased numbers and poor quality of gametes, which may eventually lead to infertility (9,10).

 
Figure 1. Some causes of infertility (45)
 
 
Figure 2. Some risk factors of female infertility (46)

Inadequate consumption of trace elements could result in deficiency of the immune system, multiple infections, more severe infections, growth retardation, late sexual maturation, and infertility (18). Magnesium (Mg) is a very much abundant mineral in the body, especially as an intracellular divalent cation, as well as in a number of metabolic reactions in the body (19,20). On the average about, 50%, 50%, and 1% of Mg are found in the bone, tissues/organs, and blood, respectively (19,20). Some of the processes in which Mg is a cofactor include the synthesis of protein, production of cellular energy, storage, reproduction, synthesis of DNA and RNA, and stability of mitochondrial membranes (21–24). The nutritional role of Se is realized by its inclusion in selenoproteins that have selenocysteine at their active center (25). Selenoproteins are involved in a number of biological processes, including but not limited to fertility and reproduction (26). As an aid in reproduction and pregnancy, glutathione peroxidase (GPx) is involved in the detoxification of peroxides (hydrogen peroxide and lipid peroxides), forming harmless products and thereby preventing damage to cell by reactive oxygen species (27). Both Se and GPx are associated with follicular fluid (28) and fertility disorders. Accordingly, this study assessed the levels of Zn, Mg, Se, and GPx in female infertility.

This is a cross-sectional design using a stratified random sampling method. Stratification was by age and diagnosis. The study was conducted at the Federal Medical Centre (FMC), Ido-Ekiti, Ekiti State (Nigeria), among women aged 21–45 and diagnosed with infertility (primary or secondary). The study investigated 50 subjects diagnosed with primary (25 subjects) and secondary infertility (25 subjects); also, 40 apparently healthy subjects were enrolled as control subjects. The subjects were informed about the research, and they voluntarily gave their consent before they participated in the study. All sample analysis was carried out in the laboratory of the Medical Laboratory Science Department of Afe Babalola University, Ado-Ekiti. Ethical approval was obtained from the Health Research and Ethics Committee of the Federal Medical Centre, Ido-Ekiti, Ekiti State. The purpose of the research was explained to each participant using an informed consent for literate participants and a verbal explanation for illiterate participants. Participants were not forced to answer questions, but at their free will. The participants were assured of confidentiality and voluntary participation and that there were no financial benefits whatsoever.

Sample Collection and Preparation

A venous blood sample of about 6 mL was collected from the cubital fossa using a needle and syringe and dispensed into a universal plain (non-anticoagulant) bottle. The blood was allowed to clot and spun down at 12,000 rpm for 5 minutes to separate the serum from the cells. The serum samples for estimation of Zn, Mg, Se, and GPx were stored at temperatures of -20^oC until analysis. Glutathione peroxidase ELISA kit was purchased from Melsin Medical Co., Limited, China and analyzed using Readwell ELISA plate analyzer from Robonik India Private Ltd., India. Magnesium reagent kit was from Teco Diagnostics, USA and analyzed spectrophotometrically using a spectrophotometer from Pioway Medical Lab Equipment Co. Ltd., China.

Analysis of Biochemical Parameters

Estimation of Zn and Se

Zn and Se were determined using an atomic absorption spectrophotometer (AAS; AAS Buck Scientific 210VGP, from BUCK Scientific Inc., USA). Zn was measured at a wavelength of 213.9 nm, while Se was measured at 313.7 nm.

Principle: Zn and Se absorb light that is emitted by the metallic cathode lamp at the corresponding wavelength. The amount of the light absorbed is proportional to the concentration of the metal in the solution, and the results were displayed on the instrument in ppm. These were converted to mg/dL for Zn and ug/L for Se, respectively (29).

Estimation of Mg

Principle: Mg reacts with calmagite in an alkaline medium to form a red-colored compound that is measured spectrophotometrically at 530 nm. The color produced is proportional to the concentration of the Mg present in the sample (30).

Estimation of GPx

Principle: GPx polyclonal antibodies, which have been pre-coated on the micro-well plates, are reacted with enzyme-labeled antibodies and patients’ serum to form antigens and antibodies sandwich complex. The antibody-bound fraction is separated from an unbound antigen by decantation and washing, after which the enzyme substrate is added for color development. The intensity of the color produced is proportional to the concentration of the GPx present in the sample (31).

Statistical Analysis

The results obtained were subjected to statistical analysis using SPSS 23 (SPSS Inc, Chicago, Ill, USA). All parameters were expressed as mean±SD. Analysis of variance (ANOVA) was the tool of choice in comparing means. A correlation analysis was also done to determine the relationship between parameters. P-values at <0.05 or <0.01 were taken to be statistically significant.