Gynecomastia is an increase in the size of the mammary gland in men. The condition can occur in one or both breasts. It starts as a small mass under the nipple, which can be sensitive. One breast can be bigger than the other. Its cause is an imbalance between the stimulatory effects of estrogen (female sex hormones) and the inhibitory effects of androgens (male sex hormones) in the breast tissue, when the first ones increase, or the second ones descend.
Gynecomastia is a problem relatively common in the population, and there are three prevalence peaks throughout life:
Newborns: Between 60 and 90% of newborns have gynecomastia, produced by the passage of maternal estrogens through the placenta. It is a transient gynecomastia that disappears in about 2-3 weeks.
Puberty: Gynecomastia in puberty affects mainly young people aged between 10 and 14 years, and is due to the transient and physiological increase in estrogen that occurs at this age.
Elderly: Is due to an increase in fatty tissue with a greater peripheral aromatization ( a process that occurs in adipose tissue and that involves the conversion of androgens into estrogens), a decrease in the production of testosterone by the testes and the use of drugs.
The correct answer for this question is this one: "c. J.J. Thompson." J. J. Thomson is the <span>scientist who designed an experiment that enabled the first successful detection of an individual subatomic particle. </span>J.J. Thomson<span> (Sir Joseph John Thomson, 1856-1940), who demonstrated in 1897 that "cathode rays" consisted of negatively-charged particles, later named electrons.</span>
Lac operon gets activated in the presence of lactose, but Trp operon gets deactivated in the presence of tryptophan.
