T2 L20 Physiology of Puberty Flashcards
Define puberty
The stage of physical maturation in which an individual becomes physiologically capable of pro-creation (sexual reproduction)
List some of the physical changes that occurs during puberty (both male + female)
Growth spurt
Secondary sex characteristics
Menarche/spermatogenesis
Between what ages do girls begin their growth spurt? How long does it last?
Age: 8 - 14 yrs
Duration: 2.5 yrs
How many cm do girls grow per year during their growth spurt?
6 - 10 cm (per year)
Between what ages do girls begin to have breast growth? What is this called?
Age: 8 - 13 yrs ( avg: 11 yrs )
THELARCHE
NOTE: This is usually the first pubertal sign
Between what ages do girls begin to grow pubic hair? What is this called?
9 - 13 yrs
PUBARCHE
What % of girls have pubarche as their first pubertal sign?
25%
Between what ages do girls begin to grow axillary (armpit) hair? What is this called?
Age: 9.5 - 15 yrs
ADRENARCHE
Between what ages do girls begin to menstruate? What is this called?
10 - 16 yrs ( avg: 13 yrs )
MENARCHE
What may adrenarche follow?
Menarche
When is H-P-G synchrony established? (in females)
Established in fetal life
What happens to GnRH release before puberty? (in females)
GnRH release is suppressed via neural mechanisms
Between what ages does mini puberty occur? What happens? (in females)
At 6-9 yrs
Pulsatile nocturnal GnRH release begins
What test is carried out to check for puberty?
A LHRH test
If this hormone is switched off the person is not experiencing puberty.
What endocrine changes occur during puberty?
Pulsatile GnRH release (nocturnal) every 90-120 min - (between 6 to 9 yrs)
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
ACTH stimulates the adrenals – Pubic & Axillary hair
What is the role of the testes?
Production of gametes (sperms)
-Sertoli cells under FSH control
Production of androgens (Testosterone)
- Leydig cells under LH control
- 95% from testes, 5% from adrenals
What is testosterone converted to in target organs?
DHT (dihydrotestosterone)
What happens in the follicular phase of the ovarian cycle?
Initially oestrogen rises (due to FSH) with LH surge in mid cycle
Ovulation occurs
What happens in the luteal phase of the ovarian cycle?
Negative feedback after ovulation
No further ovulation in the same cycle
What is the age of menarche related to?
General health
Genetic
Nutritional factors
What is happening to the mean age of menarche?
Mean age is falling at a rate of 4 months per decade
Mean age in 1840 = 16.5 y; 1990 = 12.8 y
How many girls reach menarche whilst in primary school?
1 in 8
What is the mean weight and body fat % during menarche?
Mean weight at menarche is 47.8kg
16-24% fat
NOTE: Without enough fat stores, the body does not undergo menarche
Which groups of people are likely to have a late onset of menarche?
Athletes
Patients with anorexia
Which hormone is responsible for axillary and pubic hair?
Adrenal androgens
BONUS: Which zone of the adrenal cortex produces adrenal androgens?
Zona reticularis
Which hormone stimulates the zona reticularis?
ACTH (from pituitary gland)
At what age do girls start producing DHEAS & androstenedione? At what age do girls have adequate levels of DHEAS & androstenedione?
Starts producing : 6 yrs
Adequate levels : 8 yrs
At what age do boys start producing DHEAS & androstenedione? At what age do boys have adequate levels of DHEAS & androstenedione?
Starts producing : 8 yrs
Adequate levels : 10 yrs
What test can be carried out to find out which androgens are responsible for adrenarche?
Urine profile test
What is the chronological order of puberty in girls?
1) Growth spurt
2) Breast development
3) Pubic hair
4) Axillary hair
5) Menarche
What is the chronological order of puberty in boys?
1) Testicular volume
2) Penile length
3) Pubic hair
4) Growth spurt
5) Axillary / Facial hair
6) Deep voice
Below what age does early or precocious puberty begin in girls and boys?
Girls – under 8 yrs
Boys – under 9 yrs
After what age does delayed puberty begin in girls and boys?
Girls – over 14 yrs
Boys – over 14 yrs
What is precocious puberty?
Early or Premature puberty
Presence of true pubertal features at an young & inappropriate age
Describe the two subtypes of precocious puberty
Central or True precocious puberty
-Gonadotrophin dependent
Peripheral or Pseudo-precocious puberty
-Gonadotrophin independent
What are the normal variants of precocious puberty?
Premature Thelarche : isolated breast development. Usually seen in children <2-3 yrs of age. Do a LHRH test and investigate the gonadal axis.
Premature Adrenarche : isolated pubic hair development (take caution as this can be the first pubertal sign in some children)
Name the concerns raised by early onset of puberty
Possible underlying sinister cause
-Boys – up to 80%
Emotional & pyscho-social upheaval at an inappropriately young age
Early cessation of growth leading to decreased final adult height
What is a hypothalamic hamartoma?
A benign tumour of the hypothalamus
What can a hypothalamic hamartoma lead to?
Central precocious puberty
What can high oestradiol levels be indicative of?
Activated pubertal axis
How can central precocious puberty be treated?
Long acting LHRH analog therapy
- sustained supra-physiological LHRH levels
- paradoxical cessation of gonadotrophin release
- stops further pubertal progression
What happens when the LHRH analog therapy is stopped?
Pubertal progression resumes
At what age is the LHRH analog therapy usually stopped?
10 - 12 years
What is pseudo-precocious puberty
Oestrogen and testosterone are secreted by tumours in the adrenal gland or in the testis or ovaries
The ovaries or the testes do not mature (unlike in precocious puberty)
What could be the underlying cause of iso-sexual or feminising features in pseudo-precocious puberty? (in females)
MAS (McCune-Albright syndrome) : a disorder that affects the bones, skin, and several hormone-producing (endocrine) tissues
Ovarian/Adrenal
Exogenous oestrogens
What could be the underlying cause of heterosexual or masculinising features in pseudo-precocious puberty? (in females)
CAH (Congenital Adrenal Hyperplasia)
Ovarian/Adrenal
Exogenous androgens
What could be the underlying cause of iso-sexual or feminising features in pseudo-precocious puberty? (in males)
CAH (Congenital Adrenal Hyperplasia)
Adrenal/Leydig cell tumor
Exogenous androgens
What could be the underlying cause of heterosexual or masculinising features in pseudo-precocious puberty? (in males)
Adrenal
Exogenous oestrogens
What can be the effect of androgens in females?
Androgens block the normal cycle and can cause conditions like PCOS
Describe the characteristics of delayed puberty
- Absence of true pubertal onset at an appropriate age
- Not necessarily lack of periods in a girl
- X-files – very important
BUT there are some normal variants with constitutional growth & pubertal delay
What concerns are raised by a delay in puberty?
Possible sinister underlying cause
Fear that puberty will never occur
Emotional and psychosocial upset of immaturity, especially when associated with short stature
Long term sequelae: Reduced bone mineralization
What is Klinefelter syndrome?
A chromosomal abnormality
47 XXY / Multiple X
How many male infants are affected by Klinefelter syndrome?
1 in 1000
What are the effects of Klinefelter syndrome?
Behavioural problems
Androgen deficiency
Azoospermia / Infertility
(Micro genitalia which can result in Sex change)
Lifelong testosterone replacement therapy
What is Turner syndrome?
Chromosomal abnormality
45 X (one missing X chromosome)
How many female infants are affected by Turner syndrome?
1 in 2000
Surprisingly common
What are the effects of Turner syndrome?
Triad - Short stature, streak gonads, primary amenorrhoea
Dysmorphic features – Webbing of neck, cubitus valgus
Coarctation of aorta, horse shoe kidneys
What is an early clue for Turner syndrome?
Lymphedema
How is Turner syndrome treated?
- Growth Hormone therapy
- Pubertal induction + ongoing HRT
- Active monitoring to detect co-morbidities
- Assisted conception
NOTE: Exclude co-existing congenital anomalies first
What is Kallmann syndrome?
A condition that causes hypogonadotrophic hypogonadism.
Leads to GnRH deficiency
Present at birth
What could be a sign of Kallmann syndrome in early infancy?
Undescended testicles or a small penis
Name another presentation of Kallmann syndrome
Loss of smell
How is hypogonadotrophic hypogonadism treated?
Lifelong testosterone treatment
What is the normal variant for delayed pubertal growth?
(Constitutional delayed growth & puberty)
Late onset of puberty
Bone age delayed slightly
Family history is often present
Is the normal variant for delayed pubertal growth more common in boys or girls?
BOYS
Do people that fall within the normal variant for delayed pubertal growth reach their adult height?
YES
NOTE: Pubertal induction is sometimes necessary
