Physiology of puberty Flashcards
Define puberty
The stage of physical maturation in which an individual becomes physiologically capable of precreation
- changes include: growth spurt, secondary sex characteristics, menarche/spermatogenesis
State the physical changes in girls and their average age of onset
Which one comes first?
Growth spurt (8-14 yo) - 6-10cm/year for 2.5 years
Breast growth/ Thelarche (8-13 yo)
Pubic hair/Pubarche (9-13yo)
Axillary hair/ Adrenarche (9.5-15 yo)
Menstruation/ Menarche (10-16 yo)
Thelarche first sign usually. Pubarche in 25%
What factors influence menarche?
- Related to general health, genetic and nutritional factors
- mean age reducing (1/8 start in primary school)
- body weight and fat important (mean weight at menarche 47.8kg; 16-24% fat)
- reason why athletics and anorexics have later onset
Describe the endocrine changes that occur during puberty
HPG synchrony (established in foetus)
- until puberty neural mechanisms suppress GnRH release
- at 6-9yo pulsatile nocturnal GnRH release every 90-120 minutes
- Increased GnRH–> Increased LH and FSH –> ovaries become sensitised to the effects of FSH and LH –> final phase: development of positive and negative feedback mechanism
ACTH stimulates the adrenals (zona reticularis)–> pubic and axillary hair
- DHEAS and androstenedione
- in girls begins at 6 and reaches adequate levels by 8
- in boys begins at 8 and reaches adequate levels by 10
What happens to the testes during puberty?
- Production of spermatozoa by sertoli cells under FSH control
- Production of testosterone by leydig cells under LH control (95%)
- Testosterone in blood is converted to DHT in target organs
How does the ovarian cycle change during puberty?
FOLLICULAR PHASE
- Initially E increase (FSH) with LH surge in mid cycle
- Ovulation occurs
LUTEAL PHASE
- Negative feedback after ovulation
- No further ovulation in the same cycle
State the chronological order of puberty in boys and girls
GIRLS
Growth spurt, breast development, pubic hair, axillary hair, menarche
mean duration 2-3 years; mean age 12.9
BOYS
Testicular volume, penile length, pubic hair, growth spurt, axillary/facial hair, deep voice
mean duration 3-5 years; mean age 14.6
There are disorders of puberty.
What is precocious puberty?
Signs?
Concerns?
Presence if true pubertal features as a young and inappropriate age (Less than 8 in girls, 9 in boys)
- “TRUE”: central PP, gonadotrophin dependent
- “PSEUDO”: Peripheral PP, gonadotrophin independent
SIGNS- premature thelarche, adrenarche (isolated)
CONCERNS
- possible sinister underlying problems (≥80% in boys)
- emotional and psychosocial issues at young age
- early cessation of growth leading to decreased final adult height
There are disorders of puberty.
What is a hypothalamic hamartoma?
How does it present?
Treatment?
A benign tumor caused by congenital malformation
- Blood clots in nappy, bilateral breast buds, Ht and Wt > 97th centile, enlarged uterus, mature bone age
CAUSE OF CENTRAL PERCOCIOUS PUBERTY
Treat with long acting LNRH analog therapy
- sustained supraphysiological LNRH levels
- paradoxical cessation of gonadotrophin release
- stops further pubertal progression (resumes if treatment stops)
There are disorders of puberty.
State a cause for iso sexualisation in male and females
State a cause of hetero sexualisation in male and females
FEMALES
Iso sexualising/feminising
- MAS, Ovarian/adrenal
Hetero-sexual/masculinising
- CAH, ovarian/adrenal
MALES
Iso sexualising/masculinising
- CAH, adrenal, leydig cell tumour
Hetero-sexual/feminising
- Adrenal
There are disorders of puberty.
What is the presentation of congenital adrenal hyperplasia?
Pathophysiology of congenital adrenal hyperplasia
- Obesity
- No breast bud
- Pubic hair stage 2 (prematurely)
- Low LH & FSH
- Steroid profile
21-Hydroxylase is involved in the biosynthetic pathway of both aldosterone and cortisol. These two hormones are deficient and testosterone is elevated.
There are disorders of puberty.
What is considered delayed puberty?
What is important to consider?
SIGNS/ Normal variant?
Concerns?
Delayed (>14 yo)
- Not necessarily lack of periods in a girl
- X files VERY important
SIGNS- constitutional growth and pubertal delay
Concerns
- possible sinister underlying cause
- fear that it’ll never happen
- emotional and psychosocial upset of maturity (especially in regards to short stature)
- long term sequelae: reduced bone mineralisation
There are disorders of puberty.
Klinefelter syndrome can cause delayed puberty.
State its karyotype
Presentation?
State 5 clinical signs?
Management?
- Extra sex chromosome e.g. 27 XXY/multiple X. Affects 1/1000 male infants
- No pubertal progression, learning difficulties, tall, low bone age, behavioural problems, azoospermia/infertility, microgenitalia
- Frontal baldness absent
- Poor beard growth
- Narrow shoulders
- Grow fewer chest hairs
- Breast development
- Wide hips
- Small testicular size
- Long legs
Manage with lifelong testosterone replacement therapy
There are disorders of puberty.
Turners syndrome can cause delayed puberty
How would a patient present?
- Short stature, no pubertal onset, recurrent ear infections, large carrying age, widely spaced nipples
(affects 1/2000 LIVE female births)
Diagnostic triad
- short stature
- streak gonads
- primary amenorrhoea
* ** an early clue is dyslipidaemia
Dysmorphic features include: webbing of neck, cubitus valgus
- Coarctation of aorta, horse shoe kidneys
There are disorders of puberty.
Turners syndrome can cause delayed puberty
How do you manage such a patient?
- Exclude coexisting congenital anomalies
- GH theray
- induce puberty and ongoing HRT
- active monitoring to detect comorbidities
- assisted conception
