The NIDDK reports that, throughout life, the prostate goes through two major growth stages, although according to the Frontiers in Endocrinology research, this could be considered three stages if counting mini-puberty. On average, people assigned male at birth enter the first stage of puberty between the ages of 9 and 14, according to Healthline. This is about the time when the first (or second) prostate growth stage occurs, lasting until the individual is roughly 20 years old. It’s during this time that the gland increases in weight from approximately 10 grams to 20 grams and grows to about the size of a walnut.
The prostate remains this size until about the age of 25 when the organ then enters the second (or third) growth stage. This phase doesn’t have an endpoint and continues as one ages. It’s during this growth stage that men are most susceptible to benign prostatic hyperplasia (BPH), or an enlarged prostate. By the time an individual reaches their 40s, the prostate may become apricot-sized or closer to the size of a lemon or bigger once they reach their 60s.