Demystifying Male Secondary Sexual Characteristics Development and Breast Development

A beard is a hallmark of masculinity, but 18-year-old Xiao Chen's upper lip and chin are still completely bald, with only a few fine downy hairs upon closer inspection. This makes him feel unmanly and very distressed. So why don't men grow beards? Beard growth is a manifestation of male secondary sexual characteristics. Secondary sexual characteristics are stimulated by androgens secreted by the testes after a boy enters puberty. Before the age of 11, both boys and girls have very low levels of androgens, and the physical differences between them are not significant. There is no strict time limit for puberty development in boys, generally between 10 and 14 years old.

In healthy men, the levels of androgens are generally consistent, but the amount of facial hair varies greatly from man to man. Some men have thick beards, some have sparse beards, some have full beards, and some have goatees-these are all normal variations. The amount and shape of facial hair are related to ethnicity and family genetics, which is normal and there is absolutely no need to worry about it. Whether the absence of facial hair in men is pathological depends on the overall physical development. If a man has no facial hair but his reproductive organs and the secondary sexual characteristics mentioned above are all developed normally, then it is not considered pathological.

The age at which boys begin growing facial hair varies; some start a few years earlier, some a few years later, and this is all normal and nothing to worry about. However, if a boy has entered puberty but hasn't grown facial hair, and secondary sexual characteristics are not obvious, or even if puberty has passed without development, this should be considered abnormal and requires a medical examination and treatment. Some young men write to ask why they have sparse pubic hair. They often express their concerns, feeling embarrassed by the lack of pubic hair and even reluctant to go to public baths or swimming pools. It's understandable that teenagers experience various anxieties during puberty.

Problems reflected in secondary sexual characteristics can sometimes be important indicators of endocrine system or genetic diseases, so they should not be taken lightly. Pubic hair is one of the secondary sexual characteristics, and its growth is the result of androgens stimulating pubic hair growth receptors. After puberty, male pubic hair not only gradually increases but also exhibits a typical male diamond-shaped distribution. In contrast, female pubic hair growth is the result of estrogen stimulation, so the distribution of female pubic hair is characterized by a flat upper edge and an inverted triangle shape, which is quite different from that of males. However, the absence of pubic hair in men may indicate developmental problems, especially if they are over seventeen or eighteen years old and still haven't grown pubic hair, in which case a thorough investigation is necessary.

The key is to check for any abnormalities in testicular size, penis size, facial hair, Adam's apple, and voice tone. In other words, lack of pubic hair may not be an isolated issue, but rather one of a series of signs. If multiple other abnormalities are present, it may indicate a problem with the endocrine system or chromosomes. However, if no other signs are present, it is likely due to a problem with the receptors. When the pubic hair growth receptors are defective, pubic hair is sparse and soft; when the growth receptors are lacking or insensitive to androgens, pubic hair does not grow at all. This is often accompanied by sparse pubic hair and other body hair, and may also have a family history. This simple abnormality in body hair growth has no impact on overall health or reproductive health; it is simply a physiological variation, so there is no need to worry.

Some men find their breasts have inexplicably swelled, sometimes accompanied by palpable cord-like or lumpy lumps. This causes them embarrassment and a degree of panic. What exactly is going on? Most male patients who seek medical attention for breast lumps experience a physiological phenomenon, commonly occurring around puberty and in old age, medically termed gynecomastia. Pathologically, it presents as ductal hyperplasia without acinar hyperplasia, and is generally classified into primary and secondary types. Primary gynecomastia is more common in adolescent boys and older men, primarily caused by a transient increase in endogenous estrogen or a decrease in androgens, and often resolves spontaneously.

Secondary gynecomastia is commonly seen in liver disease, testicular disease, adrenal gland disease, thyroid disease, diabetes, and tumors of the urogenital or nervous systems. Long-term use of estrogen for prostate disease, or long-term use of certain medications for other diseases, such as reserpine, isoniazid, digitalis, and chlorpromazine, can also cause breast development, which usually subsides after discontinuation of the medication. Additionally, intersex conditions and congenital testicular hypoplasia can also lead to breast enlargement. Clinically, gynecomastia is mainly characterized by bilateral symmetrical or asymmetrical breast development in 60%–80% of cases, although unilateral development (more common on the left side) is also observed. The breasts vary in size, and asymmetrical or symmetrical bulges are often visible in both breasts. In smaller cases, only flat, round nodules can be felt under the skin of the areola.

The lump is firm and resilient, with clear, regular edges, good mobility, and no adhesion to the skin. It is located concentrically with the nipple. If an eccentric lump is found, other lesions should be considered; clinically, this type of lump is called "adenomatous." Another type of developing breast tissue exhibits diffuse hyperplasia with indistinct edges, often fusing with surrounding breast tissue. No obvious nodules are palpable under the areola. Larger nodules may gradually swell to the size of a woman's breast; this type is clinically called "diffuse." Developing breasts often experience swelling, stabbing, or throbbing pain. If obvious nodules are present, tenderness or pain upon palpation is common; painless cases are rare. A few patients experience a white, milky discharge when the nipple is squeezed; spontaneous discharge is uncommon.