1.1 Puberty Flashcards
How does TRH affects gonadotrophin levels?
high TRH levels): stimulates prolactin production → stimulates dopamine release → inhibits GnRH → limits gonadotrophin (LH, FSH, oestrogen, progesterone) levels
Effect of TSH?
Stimulates T3 and T4 production
Effect of prolactin?
Stimulates milk production
Effect of GH?
Stimulates growth (in children) & maintains bone strength (in adults)
Effect of FSH?
Stimulates oestrogen production and oocyte development
Effect fof LH?
Stimulates oestrogen and progesterone production
Effect of ACTH?
Stimulate cortisol and androgen production
Effect of vasopressin?
Regulates osmolality & blood volume
Effect of oxytocin?
Triggers uterine contractions during labour
Each mature ovarian (Graafian) follicle is formed from an outer ___________ layer, and inner ___________ layer and a fluid-filled central cavity (antrum):
• Theca layer produces androgens which are converted to oestrogens in the granulosa layer (mainly oestradiol and oestrone)
As the secondary follicle grows under the influence of FSH, fluid (follicular liquor) accumulates between the granulosa cells → become confluent and forms the antrum:
• Oocyte becomes surrounded by several layers of granulosa cells, and is attached to the wall of the follicle by the ___________
• Thecal cells outside the basal lamina of the granulosa cells differentiate into the inner theca interna (pale, larger) and outer theca externa (appears like regular stroma)
• Progesterone is only produced later by the corpus luteum (after ovulation)
theca;
granulosa;
cumulus oophoricus;
What functions do oestrogens have?
- Stimulate breast development
- Promote growth and maturation of bone and pubertal growth spurt
- Increases binding globulin formation in the liver (e.g. SHBG, TBG)
- Increases HDL and reduces LDL (cardioprotective function)
- High levels stimulate LH production → triggers ovulation
What is the function of progesterone?
Progesterone is mainly involved in maintaining the pregnancy:
• Encourages secretory changes in the endometrium and encourages endometrial proliferation
• Thickens the cervical mucus to prevent sperm penetration (after fertilisation)
• Prevents uterine contractions (and other smooth muscles including in the lactiferous glands to prevent lactation during pregnancy)
where is oestrogenn synthesized and what is the synthesis mediated by?
- Peripheral conversion of androgens in adipose tissue → mediated by FSH release (in a negative feedback loop)
- Oestradiol synthesis in the ovary requires CYP450 and HSD (hydroxysteroid dehydrogenase) enzyme families
where is progesterone synthesized?
Produced by the ovaries, adrenal glands, placenta (from conversion of cholesterol → pregnenolone → progesterone) and stored in the adipose tissues
which receptors do progesterone bind to?
intracellular progesterone receptor and mineralocorticoid receptors (with greater affinity than aldosterone and cortisol → strong inhibitor)
what does thelarche means?
Start of breast development
What does pubarche means?
Development of pubic hair
what does adrenarche means?
Development of secondary sexual hair and sebaceous gland formation in the axilla and skin → sweat, body odour and skin oiliness (may cause acne)
• Due to adrenal zona reticularis maturation → androgen production (adrenal source; not gonadal source)
What does menarche means?
Onset of menstrual bleeding
How is the breast and pubic hair like at stage I puberty in girls?
- breast: only papillae elevated
- no pubic hair
How is the breast and pubic hair like at stage II puberty in girls
- Areola and breast elevated as a small mound (areola enlarged)
- Sparse downy, slightly pigmented hair mainly growing along the labia
How is the breast and pubic hair like at stage III puberty in girls
- Further enlargement of breast and areola with smooth contours
- Longer coarser hair (mostly curly) over the junction of the labia
How is the breast and pubic hair like at stage IV puberty in girls
- Areola and papilla form a contour above the breast tissue
- Pubic hair: Adult in appearance but smaller area covered and no spread to medial surface of thighs
How is the breast and pubic hair like at stage V puberty in girls
- Areola flattens in line with breast contour and only papilla elevated
- Pubic hair: Adult in appearance and quantity with spread to medial surface of thigh
which stage of puberty does maximal growth spurt occurs?
stages II and III; slower growth (~5cm/year) after the onset of menarche
which stage of puberty does menarche occurs?
stage IV
what is the definition of preconcious early puberty?
Development of secondary sexual characteristics before 8 (girls) or 9 years (boys):
what is the definition of delayed late puberty?
Absent/incomplete development of secondary sexual characteristics by 13 years in girls or 15 years in boys (mostly hypogonadism):
what are the causes of central preconcious puberty?
- Central (true/consonant/gonadotrophin-dependent) precocious puberty (CPP) occurs due to the premature activation of the HPG axis
- Causes: idiopathic (90% of girls → boys more likely to have identifiable aetiology), neurological (cerebral tumours, hydrocephalus, meningitis), cranial radiotherapy
what are the causes of perioheral preconcious puberty?
sex steroid secretion from gonadal tumours, extragonadal tissues or exogenous administration (e.g. ovarian/adrenal tumours, CAH, oestrogen administration) or genetic (e.g. McCune-Albright syndrome)
What is congenital adrenal hyperplasia and what are the signs?
Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive conditions affecting steroid biosynthesis (most commonly 21-hydroxylase deficiency):
• Signs: virilisation of female infants, enlarged penis in male infants, salt-losing crisis 1 – 3 weeks after birth (with poor weight gain, vomiting, lethargy, dehydration), precocious puberty
What is Mccune Albright’s syndrome and how does it present?
McCune-Albright syndrome is a complex genetic disorder affecting bone, skin, endocrine systems:
• Due to the unregulated production of sex steroids by the gonads (activating mutation of the G-protein complex)
• Triad of symptoms: ‘café au lait’ spots, fibrous dysplasia (of bone), endocrine hyperfunction
what is the hormone profile of central (secondary) hypogonadism?
low GnRH, low LH/FSH, low oestrogen
what are the causes of central (secondary) hypogonadism if HPA axis is intact?
- Constitutional delay of growth and puberty
- Chronic illness
- Low BMI (due to malnutrition or anorexia nervosa)
what are the causes of central (secondary) hypogonadism if HPA axis is not intact?
- Kallmann syndrome (rare genetic disorder more common in males → isolated GnRH deficiency with anosmia due to impaired migration of GnRH cells and defective olfactory bulb → similar origin)
- Hypothalamic and/or pituitary lesions (e.g. prolactinoma)
- Trauma, tumours, irradiation, hydrocephalus
what is the hormone profile of peripheral (primary) hypogonadism
insufficient ovarian production of sex steroids due to gonadal dysfunction
Hormone profile: high GnRH, high LH/FSH (no negative feedback), low oestrogen
what are the possible causes for peripheral hypogonadism?
- genetic: Turner syndrome (45X): commonest cause in women
- acquired: Damage to ovarian tissue (e.g. pelvic irradiation, chemotherapy, trauma, surgery, autoimmune, infections (mumps, TB), toxic damage (galactossaemia))
What are the features of turner syndrome?
- Common features: ovarian dysgenesis, short stature (presence of SHOX/short stature homeobox gene on X chromosome)
- Less common features (20 – 30%): neck webbing, posteriorly rotated auricles, arrow palate, cubitus valgus, widely spaced nipples
- Associated defects: cardiac (aortic coarctation, bicuspid aortic valve, aortic dilatation), renal, thyroid abnormalities (autoimmune thyroid disease) • Patients with mosaic Turner’s syndrome may have normal puberty and growth
How do patients with congenital malformations of the uterus and/ vagina present?
Affected individuals usually present with primary amenorrhoea (no menarche by the age of 16) but otherwise normal pubertal development
What is mullerian agenesis?
Absent uterus and vaginal hypoplasia due to failure of development of the Mullerian duct
What is imperforate hymen and how does it present as?
Layer of connective tissue forming a transverse septum which obstructs the vaginal opening at the level of the introitus:
• Presentation: primary amenorrhoea, cyclical abdominal pain, urinary retention
What is PCOS and how does it present as?
May present with amenorrhoea (accompanied by hirsutism, acne, central obesity)
How does preconcious puberty affect growth?
Initially tall then height becomes restricted due to early epiphyseal plate fusion (no more growth)
How does delayed puberty affect growth?
Mostly unaffected
Short in Turner syndrome (45XO)
Tall in other conditions (e.g. Klinefelter syndrome 47XXY)