The testes are the primary source of androgens and the site of spermatogenesis, with their development and function regulated by hormonal actions via endocrine and paracrine pathways. Male fertility relies on testosterone, which is essential for spermatogenesis, and follicle-stimulating hormone (FSH), which is crucial for the proliferation, differentiation, and proper functioning of Sertoli and germ cells. This review covers the research on how androgens, FSH, and other hormones support processes crucial for male fertility in the testis and reproductive tract. These hormones are regulated by the hypothalamic-pituitary-gonad (HPG) axis, which is either quiescent or activated at different stages of life. Hormonal imbalances, whether due to genetic predispositions or environmental influences, can lead to reproductive disorders such as hypogonadism or hypergonadism. Understanding the regulatory network and molecular mechanisms involved in testicular development and spermatogenesis is crucial for developing new therapeutic methods, drugs, and male hormonal contraceptives. The decline in male sperm count has been a significant global issue, with a 51.6% decrease in mean sperm concentration and a 62.3% decrease in total sperm count from 1973 to 2018. This decline is now considered a major public health concern, and the relationship between sperm count and infertility has received widespread attention. Infertility or reduced fertility can be attributed to endocrine diseases, testicular dysfunction, and poor lifestyle factors. The endocrine system serves as the primary regulator of reproductive function, and a delicate hormonal balance and crosstalk are critical for testicular development and spermatogenesis. The testes consist of multiple compartments, including seminiferous tubules, interstitial cells (Leydig cells), and supporting cells (Sertoli cells). Testis physiology involves the coordinated functioning of various cells and hormones to maintain male reproductive health and fertility. The testes produce hormones such as inhibin and estrogen, which help regulate FSH levels and play roles in testicular function. Understanding testis physiology is crucial for diagnosing and treating male reproductive disorders and infertility. The hypothalamic–pituitary–gonadal (HPG) axis is a vital system involved in hormonal regulation. It consists of the hypothalamus, which releases gonadotropin-releasing hormone (GnRH); the pituitary gland, which secretes LH and FSH; and the gonads (testes in males and ovaries in females). In males, GnRH stimulates the pituitary gland to release LH and FSH, which act on Leydig cells and Sertoli cells, respectively, to regulate testosterone production and spermatogenesis. Imbalances in these hormones can lead to decreased fertility, infertility, or other reproductive/non-reproductive system diseases. Testosterone is the primary androgen in the male body, directly affecting sperThe testes are the primary source of androgens and the site of spermatogenesis, with their development and function regulated by hormonal actions via endocrine and paracrine pathways. Male fertility relies on testosterone, which is essential for spermatogenesis, and follicle-stimulating hormone (FSH), which is crucial for the proliferation, differentiation, and proper functioning of Sertoli and germ cells. This review covers the research on how androgens, FSH, and other hormones support processes crucial for male fertility in the testis and reproductive tract. These hormones are regulated by the hypothalamic-pituitary-gonad (HPG) axis, which is either quiescent or activated at different stages of life. Hormonal imbalances, whether due to genetic predispositions or environmental influences, can lead to reproductive disorders such as hypogonadism or hypergonadism. Understanding the regulatory network and molecular mechanisms involved in testicular development and spermatogenesis is crucial for developing new therapeutic methods, drugs, and male hormonal contraceptives. The decline in male sperm count has been a significant global issue, with a 51.6% decrease in mean sperm concentration and a 62.3% decrease in total sperm count from 1973 to 2018. This decline is now considered a major public health concern, and the relationship between sperm count and infertility has received widespread attention. Infertility or reduced fertility can be attributed to endocrine diseases, testicular dysfunction, and poor lifestyle factors. The endocrine system serves as the primary regulator of reproductive function, and a delicate hormonal balance and crosstalk are critical for testicular development and spermatogenesis. The testes consist of multiple compartments, including seminiferous tubules, interstitial cells (Leydig cells), and supporting cells (Sertoli cells). Testis physiology involves the coordinated functioning of various cells and hormones to maintain male reproductive health and fertility. The testes produce hormones such as inhibin and estrogen, which help regulate FSH levels and play roles in testicular function. Understanding testis physiology is crucial for diagnosing and treating male reproductive disorders and infertility. The hypothalamic–pituitary–gonadal (HPG) axis is a vital system involved in hormonal regulation. It consists of the hypothalamus, which releases gonadotropin-releasing hormone (GnRH); the pituitary gland, which secretes LH and FSH; and the gonads (testes in males and ovaries in females). In males, GnRH stimulates the pituitary gland to release LH and FSH, which act on Leydig cells and Sertoli cells, respectively, to regulate testosterone production and spermatogenesis. Imbalances in these hormones can lead to decreased fertility, infertility, or other reproductive/non-reproductive system diseases. Testosterone is the primary androgen in the male body, directly affecting sper