Physiological Changes During Puberty PDF

# Growth and Development Module (GRD 111) ## Topic Title: Physiological Changes During Puberty ### Department of Physiology Dr. Wala AlShammari. ## Objectives - After studying this lecture, you will be able to: - Interpret the hormonal changes during puberty. - Differentiate the somatic...

# Growth and Development Module (GRD 111) ## Topic Title: Physiological Changes During Puberty ### Department of Physiology Dr. Wala AlShammari. ## Objectives - After studying this lecture, you will be able to: - Interpret the hormonal changes during puberty. - Differentiate the somatic growth and major physiological changes accompanying puberty in both sexes. - Analyze the hormonal control of puberty onset. - Pubertal disorders (precocious puberty and delayed puberty). ## Puberty - A stage of human development when sexual maturation and growth are completed and results in ability to reproduce. - Accelerated somatic growth. - Maturation of primary sexual characteristics (gonads and genitals). - Appearance of secondary sexual characteristics (pubic and axillary hair, female breast development, male voice changes...). - Menstruation and spermatogenesis begin. - Puberty means the onset of adult sexual life. - This physiological state lasts 2 to 5 years, during which the genital organs mature. - Puberty represents the first part of adolescence. ### N.B - Adolescence: is the period of life during which the child becomes an adult person. - i.e. the physical, sexual and psychological development are complete. ## Puberty- Terms and Events - Thelarche: development of breast. - Puberache: development of axillary and pubic hair. - Menarche: the first menstrual period. - Adrenarche: the onset of an increase in the secretion of androgens, responsible for development of pubic and axillary hair, body odour and acne. ## Puberty- Hormonal Changes - Hormonal changes precede physical changes. - Increased stimulation of hypothalamo-pituitary-gonadal axis - gradual activation of the GnRH (LHRH) - increases frequency and amplitude of LH pulses. - gonadotropins stimulate secretion of sexual steroids (estrogenes and androgens) - extragondaal hormonal changes (elevation of IGF-I, and adrenal steroids) ## Hypothalamic-Pituitary-Gonadal Axis - A diagram showing the interaction between the Hypothalamus, the Pituitary gland and the Gonads (Testes and Ovaries) ## Puberty- Hormonal Changes - Nocturnal GnRH pulsatility (LH secretion) precedes phenotypic changes by several years. - First phenotypic changes: - breast development / testicular enlargement. - In young children, LH and FSH levels insufficient to initiate gonadal function. - Between 9 -12 yrs, blood levels of LH, FSH increase. - Hormonal changes precede physical changes. - Amplitude of pulses increases especially during sleep. - High levels of LH, FSH initiate gonadal development. - GH secretion from pituitary also increases. - TSH (thyroid stimulating hormone) secretion from pituitary increases in both sexes: - increase metabolic rate. - promotes tissue growth. - So, the period of puberty is caused by a gradual increase in gonadotropic hormones (FSH, LH) secretion by the anterior pituitary with increased secretion of GH. - One possible cause of puberty is leptin, a hormone secreted from fat cells. Girls with high serum leptin concentrations have earlier onset of puberty. - Age of puberty: Current definitions state that puberty can be considered normal after the age of 8 years in girls and 9 years in boys. ## Puberty- Hormonal Changes (Diagram) - A diagram depicting the hormonal changes during puberty. - GnRH and GHRH in the Hypothalamus triggers the release of LH and FSH in the Pituitary gland. - LH and FSH stimulate sex steroid synthesis in the Ovary and stimulate growth hormone, which in turn triggers IGF-1 production in the liver and promotes somatic growth. ## Puberty- Female Hormonal Changes - Surge of LH release initiates 1st ovarian cycle. - Usually not sufficient to cause ovulation during 1st cycle. - Brain and endocrine systems mature soon thereafter. - Estrogen levels in blood increase, due to growing follicles. ## Puberty- Female Hormonal Changes - Estrogen induces secondary sex characteristics: - growth of pelvis - deposit of subcutaneous fat - growth of internal reprod. organs, external genitalia - Androgen release by adrenal glands increases (not as much as in male) growth of pubic hair, lowering of voice, growth of bone, increased secretion from sebaceous glands. ## Puberty: Girls - Breast enlargement usually first sign. - Menarche usually 2-3 yrs after breast development. - Growth spurt peaks before menarche. - Pubic and axillary hair growth: sign of adrenal androgen secretion. - Starts at similar stage of apocrine gland sweat production and associated with adult body odour. ## Puberty- Male Hormonal Changes - LH and FSH release increases ~10 yrs. of age. - Spermatogenesis; androgen secretion. - Adrenals also secrete androgens.. - Androgens initiate growth of sex accessory structures (e.g. prostate), male secondary sex characteristics (facial hair, growth of larynx). - Androgens cause retention of minerals in body to support bone and muscle growth. - Sertoli cells also secrete some estrogen. ## Puberty: Boys - First signs often go unnoticed. - Testicular enlargement (12-13 yrs). - 4 mL volume at puberty. - Penile and scrotal enlargement occur approx 1 yr after testicular enlargement. - Pubic hair appears at the same time. - Begins of spermatogenesis; androgen secretion. ## Timing of Puberty - Genetics: 50-80% variation in pubertal timing. - Trend toward earlier puberty exists within Western Europe and USA. - Examination of lifestyle changes may give clues regarding mechanisms inducing onset. - One of the contributing factors: nutrition. ## Nutrition - Critical body weight must be attained before activation of the reproductive system. - Even though age of menarche is decreasing, the average body weight of menarche remains the same. - Earlier puberty due to improvement of nutrition, living conditions, healthcare? - Evidence supporting hypothesis. - Obese girls go through early menarche. - Malnutrition is associated with delayed menarche. - Primary amenorrhea common in lean female athletes . ## Timing of Puberty (Diagrams) - A diagram depicting the typical timing of puberty in girls and boys, showing the different stages and the approximate age at which they occur. ## Growth in puberty ### Girls: - Growth acceleration begins at the onset of puberty. - Peak growth velocity occurs earlier (6-9 months after thelarche). - Menarche occurs after peak growth velocity. - A graph showing the growth velocity in girls during puberty, with the average age for each event marked. ### Boys: - Peak growth velocity occurs relatively late in puberty. - A graph showing the growth velocity in boys during puberty, with the average age for each event marked. ## Pubertal Disorders - A. Precocious puberty. - B. Delayed puberty. ## Abnormalities of Puberty - **Precocious puberty:** It means thelarche before the age of 8 y or menarche before 10 years in females or appearance of secondary sex characteristics before 9 y in males. - Types: - Central precocious puberty (gonadotropin-dependent). - Peripheral precocious puberty (gonadotropin-independent). - **Delayed puberty:** Secondary Sexual Characters do not develop by the age of 14 y or no menstruation till age of 16y (primary amenorrhea). - **Growth problems:** During adolescence e.g. short stature or tall stature, marked obesity and menstrual disorders at puberty.