(‘»‘THE MALE MATURATION CYCLE ‘

Now that we’ve discussed the male sexual and reproductive system, let’s explore male maturation. In the following section we will discuss the physical changes that accom­pany male puberty. Many of these changes are controlled by hormonal changes that oc­cur and contribute to physical changes in a young boy’s body. In Chapter 8 we will dis­cuss the psychosexual changes of male puberty.

Male Puberty

During a boy’s early life, the two major functions of the testes—to produce male sex hor­mones and to produce sperm—remain dormant. No one knows exactly what triggers the onset of puberty or how a boy’s internal clock knows that he is reaching the age in which these functions of the testes will be needed. Still, at an average of 10 years of age, the hypothalamus begins releasing gonadotropin releasing hormone (GnRH), which stimu­lates the anterior pituitary gland to send out follicle-stimulating hormone (FSH) and luteinizing hormone (LH; see Table 3.2 in Chapter 3).

These flow through the circulatory system to the testes, where LH stimulates the production of the male sex hormone, testosterone, which, together with LH, stimulates sperm production. A negative feedback system regulates hormone production; when the concentration of testosterone in the blood increases to a certain level, GnRH release from the hypothalamus is inhibited, causing inhibition of LH production and resulting in decreased testosterone production. Alternately, when testosterone levels decrease be­low a certain level, this stimulates GnRH production by the hypothalamus, which in­creases the pituitary’s LH production and testosterone production goes up.

As puberty progresses, the testicles grow, and the penis begins to grow about a year later. The epididymis, prostate, seminal vesicles, and bulbourethral glands also grow over the next several years. Increased testosterone stimulates an overall growth spurt in pu­berty, as bones and muscles rapidly develop. This spurt can be dramatic; teenage boys can grow 3 or 4 inches within a few months. The elevation of testosterone and DHT af­fects a number of male traits: the boy develops longer and heavier bones, larger muscles, thicker and tougher skin, a deepening voice due to growth of the voice box, pubic hair, facial and chest hair, increased sex drive, and increased metabolism.

Spermatogenesis begins at about 12 years of age, but ejaculation of mature sperm usually does not occur for about another 1 to 1-V2 years. At puberty, the hormone FSH begins to stimulate sperm production in the seminiferous tubules, and the increased testosterone induces the testes to fully mature. The development of spermatogenesis and the sexual fluid glands allows the boy to begin to experience his first wet orgasms, though, at the beginning, they tend to contain a very low live sperm count.

Andropause

As men age, their blood testosterone concentrations decrease. Hormone levels in men have been found to decrease by about 1% each year after the age of 40 (Daw, 2002). Men do not go through an obvious set of stages, as menopausal women do, but experience a less well-defined set of symptoms in their 70s or 80s called andropause. Though men’s ability to ejaculate viable sperm is often retained past the age of 80 or 90, spermatogenesis does decrease, the ejaculate becomes thinner, and ejaculatory pressure decreases. The reduction in testosterone production results in decreased muscle strength, decreased libido, easy fa­tigue, and mood disturbances. Men can also experience osteoporosis and anemia from the decreasing hormone levels (Bain, 2001). Although some men are prescribed testosterone therapy (Morales, 2004), hormonal treatment for men is still controversial today.