The gonadotropins, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and chorionic gonadotropin hormone (CG), play an essential role in reproduction. LH and FSH are synthesized in the gonadotropes of the anterior pituitary gland (or adenohypophysis), while CG is synthesized by the placental syncytiotrophoblasts. Gonadotropins, together with thyroid-stimulating hormone (TSH) synthesized by the thyrotropes of the adenohypophysis, belong to the glycoprotein hormone family. The glycoprotein hormones are complex heterodimers consisting of a common α-subunit non-covalently associated with a β-subunit, which is structurally unique in its peptide sequence for each member of the family and confers binding specificity at the receptor level. Both subunits are decorated with oligosaccharide chains, whose number can vary and that are involved in many functional aspects, including folding and secretion of the heterodimer, as well as plasma half-life and bioactivity of the hormone at the target cell. The synthesis and secretion of gonadotropins are regulated by the concerted action of several endocrine, paracrine, and autocrine factors of diverse chemical structure, the main player being the hypothalamic decapeptide gonadotropin-releasing hormone (GnRH). Gonadotropins interact with their cognate receptors (the FSH receptor and the LH/CG receptor) in the ovary and the testis. In the ovary, FSH binds to FSH receptors on granulosa cells to regulate the growth and maturation of ovarian follicles which contain the female gamete as well as stimulating estrogen production by the granulosa cells, whereas in the testes FSH stimulates the Sertoli cells lining the seminiferous tubules to initiate spermatogenesis. The target cells of LH in females are the theca cells of the ovarian follicles where it stimulates production of androgen (the precursor of estradiol) and the granulosa cells in dominant follicles where it induces the ovulatory process; subsequently, LH targets the luteinized granulosa cells of the corpus luteum where it promotes the synthesis of the sex steroid hormone progesterone, which prepares the uterus for implantation. LH stimulation of the corpus luteum is essential for the first few weeks of pregnancy until CG produced by the placenta assumes the task of maintaining the corpus luteal source of progesterone for the first trimester. In the testes, LH stimulates Leydig cell steroidogenesis, mainly testosterone production, which promotes sexual maturation and function, maintains spermatogenesis, and induces secondary sex characteristics. Mutations in the β-subunit genes of LH and FSH leading to gonadotropin deficiency are very rare. When they occur in LHβ, they are clinically manifested by lack of pubertal maturation and infertility in men and women, whereas mutations in FSHβ may lead to reduced fertility in men due to azoospermia and absent or partial puberty and infertility in women. Several natural and recombinant preparations of gonadotropins are currently available for therapeutic purposes to treat infertility. Since glycosylation is well known to vary in a cell- and tissue-specific manner, a major difference between natural gonadotropins and the currently commercially available recombinant preparations massively produced in Chinese hamster ovary cell lines, and more recently in human cell lines, lies in the abundance and nature of some of the carbohydrates that comprise the complex glycans attached to the protein core. Yet, because of the functional and pharmacological similarities between natural and recombinant compounds, both are employed in the clinical arena to treat diseases characterized by gonadotropin deficiency as well as infertility.