These stages will be different as well for those undergoing gender transition. The size of the breasts will also vary a lot from one person to another. Yes, breasts can hurt when they grow. Breasts grow in response to the hormones estrogen and progesterone. As you enter puberty, levels of these hormones increase. Your breasts begin to grow under the stimulation of these hormones.
Important Hormones Involved in Breast Growth – Must Grow Bust
Estrogen , or oestrogen , is the primary female sex hormone. It is responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens in females that have estrogenic hormonal activity: estrone , estradiol , and estriol. The estrane steroid estradiol is the most potent and prevalent of these. Estrogens are synthesized in all vertebrates  as well as some insects.
The amount of breast growth you can anticipate will vary greatly, just as it does with cisgender women. Cisgender is a term for those people whose gender assigned at birth matches their gender identity. The breast tissue growth usually takes two years to reach maximum size. These changes are induced by an increase in the ductal system behind the nipple and it is a part of the transition process that will typically normalize in a matter of months.
Women going through menopause may feel anxious about losing muscle mass, the hourglass figure they had in their 20s and 30s. Skin around the breasts becomes more elastic, causing them to shrink or sag, while weight stubbornly clings to the midsection. Estrogen known as the female hormone, plays a starring role in the development of feminine traits, including breast size. With estrogen replacement therapies so readily available on the market, many women wonder if using these treatments will help fill out their bust line.