Puberty – Physiology & Disorders Flashcards
Definition of Puberty
The stage of physical maturation in which an individual becomes physiologically capable of pro-creation (sexual reproduction).
Physical changes in Puberty
- Growth spurt (A growth spurt is a time which a person has a more intense period of growth.)
- Secondary sex characteristics
- Menarche/spermatogenesis
Physical changes in girls
1. GROWTH SPURT (8 - 14 yrs), 6 - 10 cm / yr peak 2.5 yrs duration
- The first clinical sign of puberty is (Thelarche), in thelarche is BREAST GROWTH 8 - 13 yrs (11 yrs ) . breast development in anyone below the age of 8 will be a sign of premature puberty. breast budding over the age of 13 will be a delay of puberty.
3. PUBIC HAIR (9 - 13 yrs) (Pubarche) 1st Pubertal Sign in 25%
4. AXILLARY HAIR (9.5 - 15 yrs) (Adrenarche) May follow menarche. this does not depend on pubertal hormones themselves, it depends on the activation of the adrenal gland that secretes the adrenal hormone such as androgens responsible for pubic and axillary hair.
5. MENSTRUATION 10 - 16 yrs ( 13 yrs ) (Menarche) (last to happen)
after menstruation, we will know that there will not be much growth left after menstruation has happened.
Endocrine changes in puberty
- The axis that is responsible for pubertal development is the hypothalamic–pituitary–gonadal axis (HPG axis) and this establishes in foetal life.
- There are 2 phases at which this axis is present and active
- in between those 2 phases, it’s usually non active.
-The fetal activation of the axis then seen in the mini puberty which happens in the neonatal phase and in the first six months of life.
- In cases where you have endocrinological problems, we check the active nation of the H-P-G axis and if that is present, then we know that it’s healthy.
- we then wouldn’t want to investigate the H-P-G axis in between that phase and again the periubertal phase because wouldn’t find much signalling activity going on there and we can then go and investigate it around the ages of 6-9 years where suddenly we have a release of pulsatile nocturnal GnRH .
Endocrine changes in puberty con’t
- Pulsatile GnRH release (nocturnal) every 90-120 min - 6 to 9 y
- The Pulsatile release of GnRH will then signal the rise of pituitary FSH and LH and the gonadtrophins will then signal to the ovaries and testes.
- Once they become sesitised to the effects of LH and FSH, the final phase of developing the
- Increased GnRH leads to increased FSH and LH
-Ovaries/testes become sensitized to the effects of FSH and LH
-Final phase: development of positive/negative feedback mechanism
Testes
-Production of gametes (sperms) by Sertoli cells under FSH control.
- Production of androgens (Testosterone) by Leydig cells under LH control.
- 95% from testes, 5% from adrenals
- When we have Testosterone in blood, it is converted to Dihydrotestosterone (DHT) in the target organs.
- In the boy and in start of puberty, we know that the volume of the testicular volume of testosterone is important of the clinical assessment.
- so if the testes is elarging, that is also a sign of its function.
- when we examine a size for query Precocious (early) puberty, we have to examine testicular volumes and a volume above 4mls, signals the start of puberty. a volume below that signals that this is probably not a start of true pubety. we do thois assessment clinically utilising an orchidometer (the beads) with different testicular volumes.
The Ovarian cycle
- The ovarian cycle have a follicular phase in which initially there is a rise via FSH stimulation and then LH surge in the middle of the cycle and the ovulation occurs.
- we then have the luteal phase in which there is a negative feedback after ovulation has occured and no nfurther ovulation will happen in the same cycle.
- Progesterone rises in the Luteal phase where the endometrial later increase its thickness.
- The menstrual period will haoppen at the end of the luteal phase due to the shedding of the endometrium.
The Ovarian cycle
Follicular phase
- Initially Estrogen rises (FSH) with LH surge in mid cycle
- Ovulation occurs
Luteal phase
- Negative feedback after ovulation
- No further ovulation in the same cycle
Normal Ovarian cycle
-You always have a Peak ;LH surge in the middle when there is ovulation.
Age of Menarche
- Related to general health, genetic and nutritional factors
- Mean age is falling at a rate of 4 months per decade
- Mean age in 1840 = 16.5 y; 1990 = 12.8 y
- One in 8 girls now reaches menarche while at primary school
- Body weight and % fat is also important
- Mean weight at menarche is 47.8kg
- 16-24% fat
- Athletes, patients with anorexia – late onset
Adrenarche
-The drenal androgens are responsible for axillary and pubic hair
-ACTH stimulates in the zona reticularis of the adrenal cortex stimulates this progression
-DHEAS (dehydroepiandrosterone) & Androstenedione
Girls – starts by 6, adequate levels by 8.
Boys – starts by 8, adequate levels by 10
-However, you can have premature adrenarchy. this is more common now due to the rise in obesity and early menarchy.
Chronological Order of puberty
Girls
- Growth spurt
- Breast development
- Pubic hair
- Axillary hair
- Menarche
Boys
- Testicular volume
- Penile length
- Pubic hair
- Growth spurt
- Axillary / Facial hair
- Deep voice
*(girls have an earlier growth spurt), boys grow taller later than girls.
Summary
Disorders of Puberty
Early or Precocious puberty;
Girls – under 8 yrs (having a breast development under 8 is a sign of early puberty)
Boys – under 9 yrs (having a testicular volume under 9 is a sign of early puberty)
Delayed puberty
- Girls – over 14 yrs (lack of breast development)*
- Boys – over 14 yrs (lack of testicular development)*
Precocious Puberty
Early or Premature puberty
-Presence of true pubertal features at an young & inappropriate age. This can be either because of a central cause or a peripheral cause.
1. Central or True precocious puberty
-Gonadotrophin dependent
2. Peripheral or Pseudo-precocious puberty
Gonadotrophin independent
-so there is some other source of hormone imbalance that looks like puberty but arenmt true puberty.
Normal variants
Premature Thelarche (breast development)
Premature Adrenarche (pubic/axillary hair development)
Hypothalamic hamartoma
Emileigh, 14 months old baby.
- Blood clots in nappy
- Bilateral presence of breast buds
- Height & Weight >97th centile (significant increasxe in leght and weight)
- LH= 2.2, FSH = 3.2, (both very high)
- 17β estradiol 432 (high)
- Uterus – enlarged
- Bone age – 2.8 yrs (advanced by almost a year and half)
- MRI scan attached.
*This is a case of an infant presenting with premature true puberty. You can see that the baseline LH and FSH are high when at that stage, they should be undetectable.
- You can also see that there has been an exposure to estradiol because the uterus has enlarged.
- Estrogen makes bone grow faster and longer and that’s why the baby’s bone age is advanced.
- It was the hypothalamic hematoma that troggered the early puberty. and this is one of the most common cause of early puberty in boys and girls.
Congenital Adrenal Hyperplasia
*A condition that causes you to have higher androgens
- It is a congenital disorder caused by a defect in a gene that will trigger the make of a protein that would be involved in the steroid biosynthesis pathways.
- You could have different tyoes of gene abnormalities but the most common one is 21 hydroxylase defeciency. this deficinecy causes a rise in androgen pathways and blocks the cortisol and Aldosterone pathway.
- This is usually diagnosed in the lab with a rise in 17 OHP which is
-Mairna, 6 yrs
- Obese
- Pubic hair stage 2
- No breast bud
- LH <1, FSH 1.4,
- 17β estradiol 32
- Steroid profile
Chromosomal abnormality causing delayed puberty in boys; Klinefelter Syndrome
Klinefelter syndrome (KS), also known as 47,XXY is the set of symptoms that result from two or more X chromosomes in males. The primary features are infertility and small poorly functioning testicles. Often, symptoms are subtle and subjects do not realize they are affected.
-Steven, 16 yrs
- lack of pubertal progress or abnormal pubertal progress
- Learning difficulties
- Tall stature, 98th centile
- reduced testiculalr volumne
- PH-2, G-2, TV-6ml
- LH 12, FSH 16, T 40
- Bone age – 14.5 yrs (reduced)
- Karyotype attached
Klinefelter Syndrome
•1 in 1000 male infants
- 47 XXY / Multiple X
- Behavioural problems
- Androgen deficiency
- Azoospermia / Infertility
- (Micro genitalia ® Sex change)
- Lifelong testosterone replacement therapy
Turner Syndrome
Turner syndrome, a condition that affects only females, results when one of the X chromosomes (sex chromosomes) is missing or partially missing. Turner syndrome can cause a variety of medical and developmental problems, including short height, failure of the ovaries to develop and heart defects.
-Rosie, 12 yrs
- Short Stature
- No pubertal onset
- Recurrent ear infections
- Increased carrying angle
- Widely spaced nipples
- LH 56, FSH 95,
- 17β estradiol 45
- Karyotype
Turner Syndrome
- 1 in 2000 live female births
- Triad - Short stature, streak gonads, primary amenorrhoea
- Dysmorphic features – Webbing of neck, cubitus valgus
- Coarctation of aorta, horse shoe kidneys
- Early clue - Lymphedema
- Surprisingly normal !!!
- In Turner Mosaic
