**Abstract**

Gonadal Steroids hormones play an important role in the reproductive and non-reproductive systems. Estrogen has important rule in cardiovascular system as it has vasodilator effect and reduces or prevents platelet activation. In addition, it improves the profile of circulating lipoproteins. All of which may explain why women at premenopausal age are less likely to have heart disease than menopause women or men. E2 play a grate effect on the skeletal system as it is one of the strongest regulators of osteoblast and osteoclast function, and it is responsible for the reduction of adipose tissue and regulation of the body weight, and also has dermatological effect,hence it stimulates the proliferation of keratinocytes and prevents their apoptosis, in addition to the progesterone which increases collagen synthesis. Estrogen is necessary for the functioning and integrity of the tissues of the urinary system specially of the lower urinary tract. Sex steroid are crucial for nervous system, as progesterone is important for production of neurosteroid, and estrogen is currently used in Parkinson's and Alzheimer's disease because of its effects on mental health. The androgens also have a crucial biological effects on neural, muscle, bone, adipose tissue,prostate, cardiovascular, haemopoietic, and the reproductive systems. The gonadal steroid hormones play an important role in immune system and regulating the immune response against different viral or bacterial infections.

**Keywords:** sex hormones, cardiovascular, brain, bone, urinary tract, immunity

## **1. Introduction**

Gonadal Steroid hormones (GSH) play an important role in reproductive and non-reproductive systems. As this effect occurs early in the fetus' life, gonads are initially present at the fifth weeks and developed on the medial surface of mesonephric ridges.

Therefore, sexual development and discrimination are depending on the type of hormones and gonads that present. GSH play an important role in determining sexual function and behavior. Structures of the central nervous system, such as the hypothalamus, midbrain, amygdala, cortex and anterior pituitary gland, contain androgens and estrogen receptors. The GSH must bind to specific receptors to produce cellular response. While binding of receptor antagonists generally lead to inactivation of these receptors [1].

This chapter explain the effect of sex hormones on the human body and the differences in their action in both genders.
