Draw outline of biochemical pathways indicating synthesis of human sex hormones from cholesterol. Enlist three functions of estrogen.

Introduction

Human sex hormones like estrogen, progesterone, and testosterone are steroid hormones synthesized from cholesterol. This synthesis involves a series of biochemical steps occurring primarily in the adrenal cortex, ovaries (in females), and testes (in males). Understanding this pathway helps explain how sex hormones regulate reproduction, growth, and development.

Outline of Biochemical Pathway for Sex Hormone Synthesis

The synthesis of sex hormones begins with cholesterol and proceeds through several intermediate steps:

1. Cholesterol
   • Converted into Pregnenolone by the enzyme cholesterol desmolase (side-chain cleavage enzyme, CYP11A1).
2. Pregnenolone
   • Can be converted into progesterone or 17-hydroxypregnenolone.
3. Progesterone
   • Precursor to both androgens and corticosteroids.
4. 17-Hydroxypregnenolone → Dehydroepiandrosterone (DHEA)
   • DHEA is converted into androstenedione.
5. Androstenedione
   • Can be converted into testosterone.
   • With the help of aromatase enzyme, testosterone is converted into estradiol (a type of estrogen).

Summary Pathway:

Cholesterol → Pregnenolone → Progesterone → DHEA → Androstenedione → Testosterone → Estrogen

Three Functions of Estrogen

Estrogen is the primary female sex hormone responsible for many physiological processes, especially in the reproductive system.

1. Regulation of Menstrual Cycle:
   • Estrogen helps in the growth and development of the endometrial lining during the menstrual cycle.
   • It also regulates the release of LH and FSH by feedback to the pituitary gland.
2. Development of Secondary Sexual Characteristics:
   • Estrogen promotes the development of breasts, widening of hips, and pubic hair growth in females during puberty.
3. Bone Health:
   • Estrogen helps in maintaining bone density by preventing bone resorption.
   • This is why post-menopausal women are at higher risk of osteoporosis due to estrogen deficiency.

Conclusion

The synthesis of sex hormones from cholesterol is a complex but well-regulated biochemical process. Estrogen, one of the key end products, plays vital roles in reproductive health, development, and maintaining bone strength. Disruption in this pathway can lead to hormonal imbalances and related disorders.