How Normal Breast develops:

All girls have same size of breast tissue in childhood. At the time of puberty i.e. beginning of genital development female hormone estradiol, adrenal hormone androstenidione, 17-oh Progesterone, DHEAS, Growth hormone, LH, FSH, increases & SHBG decreases, Thyroid Hormone also plays the role. These hormones changes lead to increased concentration of Free Testosterone, DHT & some more hormones. These hormones then act on the various sensors (called receptors) in the breast tissue. After the interaction of hormones & receptors certain changes occurs in the functioning of cells of breast tissue so that breast cells starts growing in thickness & size & more & more fat starts depositing in the breast . thus breast size gradually starts increasing. Simultaneously it also increases the blood supply to breast tissue leading to more availability of growth factors to the breast tissue resulting in faster growth of breast tissue. These hormones & growth factors are in high concentration during peak of secondary genital characters development i. e. puberty leading to persistent stimulation of breast tissue for next two to three years i. e. up to completion of genital development. Thus in normal girls in two to three years full breast develop.

Causes of Small Breast:

Female hormones deficiency i.e. estradiol in body due to many of the below mentioned causes as leading to absence of estrogen production (hypogonadotropic hypogonadism). Craniopharyngioma

2) Second cause for small breast is resistance of breast tissue to normal level of female hormone in the body. So that even though female hormone is normal in the body, but the breast tissue of these girls do not have sufficient receptors for female hormone leading to insufficient estrogen action meaning that female hormone is unable to work & breast do not grow well. But when female hormone level is further increased by female hormone replacement treatment & certain more medicines are given so that female hormones becomes more effective on breast, then breast tissue starts growing. Breast size then fully normalizes in six months to one-year time.

3) Growth factor deficiency

4) Zinc Deficiency

5) Estrogen biosynthetic defects

6) Congenital adrenal hyperplasia

7) Congenital absence of breast bud

8) Lipoatrophy generalized

9) DSD : Disorder of Sexual Differentiation

10) Absence of estrogen receptors in breast tissue

12) Growth hormone deficiency due to hypopituiarism, pituitary disorders

13) Progeria

12) DRUGS: Cytotoxic Agents, Cyclophoamide, Vincristine,Ionising radiation, Azathioprine

13) Overmastectomy

14) Structural Defects Of body fat cell so that they do not grow

15) Generalized hypoplastic syndrome

16) Dysmorphic Syndrome

17) Hyper Androgenism : High Androgen due to various causes leads to small breast size.