Review of Changes During Adolescence

Adolescence is a time of major physiologic, psychological, and sociologic changes, a time of transition into adulthood. It is also a time when certain diseases, developmental or infectious, tend to develop. The period of adolescence is generally considered to begin with the development of secondary sex characteristics around the age of 10 to 12 years and to continue until physical growth is completed at about age 18. The term puberty indicates the onset of reproductive changes, beginning with the appearance of secondary sexual characteristics and the first menstrual cycle in females. Both the timing and the extent of change vary greatly among individuals. In recent years, perhaps because of improved nutrition, maturation has tended to occur at an earlier age.

The biologic changes typical of adolescence result primarily from hormonal activity stimulated by the hypothalamus and pituitary gland. Gonadotropin releasing hormone (GnRh) from the hypothalamus stimulates and increases the release of gonadotropins from the pituitary. Gonadotropins (LH and FSH) support the further development of the ovaries and testes. In the female, the ovaries release ova and the sex hormones estrogen and progesterone, and in the male, the testes begin to produce sperm and to release testosterone. Although these sex hormones are produced in small quantities by the adrenal cortex during all stages of life, the larger quantities now available from the gonads are responsible for the unique types of growth and development that are characteristic of the teen years.

Linear growth is accelerated during the typical adolescent growth spurt. In most males the growth spurt occurs later than in females and usually lasts longer because epiphyseal closure is delayed in males. In recent generations both males and females have achieved a greater average height. Any growth retardation usually is apparent before adolescence, but if it is evident at this time it can be confirmed by x-rays illustrating an abnormally thin epiphyseal plate or disc. Other skeletal changes include the development of a broader pelvis in females and an increase in the width of the shoulders and chest in males. Because of the anabolic actions of the male sex hormones (androgens) or testosterone, males develop more skeletal muscle mass than females during puberty. This is obvious in the shoulder and chest areas. In a newer form of substance abuse, synthetic androgens, the “muscle-building” steroids, are taken by some adolescents to improve body image and athletic performance, without regard for dangerous side effects on the heart and liver. The growth changes of adolescence do not occur simultaneously. Limb growth occurs first, then hip and shoulder development, and increase in skeletal muscle mass is last. This is why the adolescent may appear awkward and gangly for a time until proportionate and complete maturation is accomplished.

Additional factors influencing growth during this period include nutrition, genetic factors, and activity levels. It is most important that calcium and vitamin D intake be adequate during this period. It has become evident that the risk of osteoporosis later in life is influenced by maintaining sufficient calcium intake from childhood and throughout life. Unfortunately, dietary intake often becomes erratic during this period just when demand is higher for iron, protein, and other nutrients. Therefore it is essential for the adolescent to maintain basic nutritional requirements.

With increasing body dimensions, there is an associated increase in blood volume and in the strength of cardiac contractions, although the pulse rate diminishes. Both cardiovascular and pulmonary functions reach adult values during adolescence, but usually they do not keep pace with musculoskeletal growth, leading to decreased exercise tolerance and marked fatigue at times in active teens. The basal metabolic rate gradually declines to adult levels during this period.

Obesity and Metabolic Syndrome

Recent research has shown that the ability to burn fat during exercise declines after puberty. This metabolic change along with changes in activity and diet can lead to obesity during adolescence. Not only is obesity a significant factor in the teen’s self-image, it also constitutes a major threat to their health and leads to pathophysiologic changes in metabolism that predispose the teen to diabetes and cardiovascular disease as well as permanent joint damage.

Overweight refers to and excess amount of body weight that may be a result of muscles, bone, fat, and water.

Obesity refers to an excess amount of body fat. Overweight and obesity are due to a caloric imbalance. This imbalance may be due to more calories consumed than expended, and can also be affected by various genetic, behavioral, and environmental factors.

Alarm has been expressed regarding the recent increase in obesity in children and teens. In the 6- to 11-year age group, the number of obese children has doubled between 1980 and 2000, whereas the number in the 12- to 19-year group has tripled. Obesity in children 6 to 11 years (in the United States) has risen from 7% in 1980 to 18% in 2010. Obesity in the 12-19 age group has risen from 5% in 1980 to 18% in 2010. Accompanying this significant trend is a marked increase in children and young adults with type 2 diabetes mellitus, elevated blood cholesterol/lipid levels, and increased blood pressure. The prevalence of psychological problems is also higher in obese children. Because many obese children continue to be obese adults, these conditions will lead to a higher incidence of cardiac problems, strokes, and musculoskeletal problems such as osteoarthritis. The increased obesity in children and young adults appears related to increased intake of high fat and high carbohydrate snacks, high sugar soft drinks, and “fast foods” in conjunction with decreased exercise and activity related to excessive time spent watching television or playing computer games. It is recommended that nutritious, healthy snacks and meals as well as increased regular physical activity be encouraged. This will also promote general health, growth, and development of the body. A child’s body mass index (BMI) calculated from the height and weight should be monitored if unusual weight gain is noticed.

Musculoskeletal Abnormalities