6.3 Endocrine System Changes
Learning Objectives
- Identify physical transformations in adolescence related to sexual maturation.
- Describe the effects associated with early and late onset of puberty, and how they differ for boys and girls.
- Explain the climateric, it’s impact on life and sexuality in midlife, and differing impacts of aging on women and men.
Puberty and Adolescence
Puberty is a period of rapid growth and sexual maturation. These changes begin sometime between age eight and fourteen. Girls begin puberty at around ten years of age and boys begin approximately two years later. Pubertal changes take around three to four years to complete.
One of the hallmark features of puberty is the development of sexual maturity. Primary sexual characteristics are changes in the reproductive organs. For females, primary characteristics include growth of the uterus and menarche or the first menstrual period. The female gametes, which are stored in the ovaries, are present at birth, but are immature. Each ovary contains about 400,000 gametes, but only 500 will become mature eggs (Crooks & Baur, 2007). Beginning at puberty, one ovum ripens and is released about every 28 days during the menstrual cycle. Stress and higher percentage of body fat can bring menstruation at younger ages. For males, this includes growth of the testes, penis, scrotum, and spermarche or first ejaculation of semen. This occurs between 11 and 15 years of age.
Secondary sexual characteristics are visible physical changes that signal sexual maturity but are not directly linked to reproduction. For females, breast development occurs around age 10, although full development takes several years. Hips broaden, and pubic and underarm hair develops and also becomes darker and coarser. For males this includes broader shoulders and a lower voice as the larynx grows. Hair becomes coarser and darker, and hair growth occurs in the pubic area, under the arms and on the face.
Effects of Pubertal Age
The age of puberty is getting younger for children throughout the world, referred to as the secular trend. According to Euling et al. (2008) data are sufficient to suggest a trend toward an earlier breast development onset and menarche in girls. A century ago the average age of a girl’s first period in the United States and Europe was 16, while today it is around 13. Because there is no clear marker of puberty for boys, it is harder to determine if boys are also maturing earlier. In addition to better nutrition, less positive reasons associated with early puberty for girls include increased stress, obesity, and endocrine disrupting chemicals.
Cultural differences are noted with African American girls enter puberty the earliest. Hispanic girls start puberty the second earliest, while European-American girls rank third in their age of starting puberty, and Asian-American girls, on average, develop last. Although African-American girls are typically the first to develop, they are less likely to ex