The study found that people who can conceive naturally have higher blood levels of the hormone kisspeptin and other reproductive hormones than those who are infertile, and that certain genetic variations in the kisspeptin gene are linked to lower hormone levels and infertility.

Kisspeptin, a peptide hormone, plays a pivotal role in fertility and neuroendocrine regulation of hypothalamo-pituitary-gonadal axis. Increased kisspeptin and reproductive hormones are responsible for fertility in male and females. This study aimed to explore the role of kisspeptin on hypothalamo-pituitary-gonadal axis by comparing the levels of kisspeptin in fertile and infertile subjects and identifying single nucleotide polymorphisms (SNPs) of KISS1 gene in exon 2 and exon 3 of infertile male and female cohorts. A cross-sectional study was carried out on 80 males (44 infertile and 36 fertile) and 88 females (44 in each group). Significantly high levels of kisspeptin (KP), follicle-stimulating hormone (FSH), luteinizing hormone and testosterone were observed in fertile male and female subjects except low FSH levels in comparison with infertile female subjects. One polymorphism in exon 2 (E1225K [G/A 3673]) and three in exon 3 (P1945A [C/G 5833]; Insertion of T at 6075; G2026G [C/G 6078]) in infertile group were detected, with low KP and hormonal levels. Male subjects had abnormal sperm parameters and unsuccessful attempt of intracytoplasmic sperm injection in females. Expression of SNP in exon 2 and exon 3 of KISS1 could be responsible for alteration in release of reproductive hormones and gonadal functions, hence causing infertility.