Puberty Flashcards
What is puberty?
- The period of age at which a person is first capable of sexual reproduction of offspring
- Begins in late childhood
- 8-13 years for females
- 9-14 years for males
- Characterised by maturation of the hypothalamic pituitary gondal axis
What occurs during puberty?
- Appearance of secondary sex characteristics:
- Physical growth
- Sexual development
- Psychological development
- Acceleration of growth
- Mass and fat distribution
- Bone maturation
- Adult height
- Capacity for fertilisation
- Spermatogenesis
- Ovulation
Whar are the hormonal changes in puberty?
- Adrenarche - adrenal gland component of puberty = the activation of production of androgens by the adrenal cortex, begins before age 8. responsible for the appearance of puvbic and auxillary and acne (Pubarche)
- Gonadarche - the ovary or testes component of puberty = the activation of the gonads by the pituitary hormones FSH and LH. Responsible for the production oestrogens and testosterone. Sexual maturation and development of reproductive maturity
What is the physiology of puberty?
- GNRH is a hypothalamic tropic hormone that stimulates the secretion of gonadotropins (LH-FSH)
- Hypothalamus releases GnRH in bursts occuring at approx 2-hr intervals
- This causes rates of FSH and LH secretion to rise during bursts and fall between bursts
- At the beginning of puberty , pulsatile GnRH secretion rises dramatically in response to a change in brain activity that alters neural input to the hypothalamus
What is the hypothalamus GnRH release pathway?
- Pre-puberty : hormornal feedback/ central neural suppression of GnRH release suppress onset of puberty
- Hypothalamus-piuitary-gondal axis starts working in foetus. After bitrth, sex hormones and FSH/LH found in adult levels
- Levels reduce in months after birth; pulsatile GnRH reduces in childhood and increases in frequency and amplitude before puberty
- In males - negative feedback mechanism driven by circulating gonadal steroids and inhibin which results in reciprocal changes in the secretion of pituitary gonadotropins
- Testosterone and estradiol in the male have independent effects on LH secretion
- Inhibition of LH by testosterone requires aromatization for its piuitary effects, and estradiol-induced negative feedback on LH occurs at the level of the hypothalamus
- In the female - cyclic secretion involves a positive feedback mechanism driven by oestrogens, of sufficient duration
- This initiates the synchronous release of LH and FSH that is characteristic of the normal adult woman before menopause
What is the timing and onset of puberty modulation?
- Genetic factors : 50-80% of variation in pubertal timing
- Balance in the inhibitory and excitatory factors through coordinated changes in transsynaptic anf glial-neuronal communication
- Glial cells affect GnRH secretion through growth factor- dependent cell-cell signalong coordinated by numerous unrelated genes
- Environmental factors
- e.g nutritional status ( obese are more likely to be earlier), excessive exercise
- Alteration of body metabolism linked to energy metabolism may affect the CNS restraints on pubertal onset
- Pyscohological factors
- Things like stress or anxiety can also affect the CNS control of the onset of puberty
What is Tanner stage?
- a way to classify the time, course and progress of changes that occur during puberty
- Based upon attainment of secondary sex characteristics:
- Genital development in males
- Breast development in females
- Pubic hair development in both genders
Describe female development during puberty.
1.) Thelarche :
- development of the breast
- Under the control of oestrogens
- Breast bud appears at an average age of 9 years
- Starts and completed in ~ 3 years
- Ductal proliferation
- Site specific adipose deposition
- Enlargement of the areola and nipple
- Prolactin, glucocoticoids and insulin
2.) Pubarche - growth of pubic and axillary hair
- under the control of androgens
- occurs at age 12.5 years
3.) Growth spurt
- Under the control of oestrogens
- Global process involving skeletal growth rate
- Muscle mass
- Growth of all internal organs
4.) Menarche
- Daily rise of oestradiol
- First menstrual bleeding
- It is observed 2-3 years adter thelarche
Describe the stages of male development.
- Enlargement of testes
- Followed by scrotum pigmentation and thinning of scrotal skin
- Penis enlarges
- Pubic hair develops
- Growth spurt
- Breaking of the voice at the time of puberty is indicative of androgen-induced enlargement of the larynx
What is an orchidometer?
- Helps to determine testicular volume
- Prepubertal - 1-3ml
- Pubertal - 4-12 ml
- Adult - 15-25 ml
- Can be first indicators of some disorders
- Hypogonadism (small testes)
- Fragile X syndrome (large testes)
What are some disorders of puberty?
- Precocious Puberty
- Delayed Puberty
What is precocious puberty?
- Premature sexual development before:
- 8 years in females
- 9 years in males
- Dominant in girls, usually idiopathic
- Rarer in boys, underlying lesion
- Divided into :
- Gonadotropin-dependent precocious puberty (GDPP or true):
- involves the premature activation of the hypothalamic- pituitary- gonadal (HPG) axis
Gonadotropin- independent precocious puberty ( GIPP or pseudo):
The presence of sex steroids is independent of pituitary gonadotropun release.
What is the treatment of precocious puberty?
GDPP :
- dependent on the cause of puberty : Identifiable CNS lesion, therapy is directed toward the underlying pathology
- Primary treatment option = GNRH antagonist which slows accelerated puberty and improves final height
- Dependent on child’s age - the rate of pubertal progression - height velocity - rate of bone advancement
GIPP:
- Does not repsond to GnRH antagonist therapy. Treatment is directed at the underlying pathology
- Children with tumours of the testis, adrenal gland and ovary treated by surgery.
- HCG- secreting tumours combination of surgery, radiation therapy and chemotherapy depending upon the site and histologic type
What is inomplete puberty?
- isolated manifestation of precocity without development of other signs of puberty
- Premature thelarche : Transient condition of isolated breast development in the first 2 yrs of lifem often persists for 3-5 years , and is rarely progressive. Mostly idiopathic
- Premature pubarche : Appearance of sexual hair before the age of 8 yrs in girls, or 9 years in boys without other evidence of maturation
- Premature menarche : isolated vaginal bleeding in the absence of other secondary sexual characteristics. Very rare.
What is delayed puberty?
- indicated if no signs of puberty are observed in a girl by 14 and in a boy by 15 years
