Reproductive Endocrinology Flashcards
Subtype of hormones?
- Proteins and peptide hormones e.g. insulin
- Steroid hormones e.g. testosterone, oestrogen, progesterone
- Amino acid derived hormones e.g. adrenaline, thyroxine, melatonin
Types of hormone receptors?
- G-protein coupled receptors
- Receptor tyrosine kinase
- Receptors associated with tyrosine kinase activity
- Steroid hormone receptors
How do steroid hormone receptors work?
Hormone binds to receptor –> steroid/receptor complex binds to DNA response elements –> change in gene transcription
What is the hypothalamic pituitary gonadal axis?
Hypothalamus produces GnRH which stimulates the anterior pituitary to produce LH and FSH
LH and FSH act on the testes and ovaries to produce oestrogen, testosterone and progesterone
Negative or positive feedback loop to the ant. pituitary and hypothalamus
What stimulates GnRH secretion?
Kisspeptin
Describe prolactin secretion?
Prolactin is secreted from the anterior pituitary and is under tonic inhibition from hypothalamic dopamine
Prolactin is responsible for…
breast development and lactation
Possible causes of high prolactin?
Prolactinoma
Pituitary tumours
Drugs e.g. antipsychotics and dopamine agonists
Overview of steroid hormone synthesis?
LH binds to Leydig and Theca cells which increases expression of StAR which promotes cholesterol transfer to the inner mitochondrial membrane and initiates steroidogenesis
Cholesterol converted to pregnenolone which is then converted to oestrogen, progesterone or testosterone
Where is testosterone produced?
Leydig cells in the testes
What converts testosterone to dihydrotestosterone?
5-alpha reductase
What is the most biologically active form of testosterone in the body?
Dihydrotestosterone
Where is oestrogen produced?
Granulosa and Theca cells of ovaries
Corpus luteum
Where is progesterone produced?
Corpus luteum
Placenta in pregnancy
Adrenal gland
What is oligoamenorrhoea?
reduction in frequency of periods to <9 per year
What is primary amenorrhoea?
failure of menarche by 16 years
What is secondary amenorrhoea?
cessation of periods for >6 months in an individual who has previously menstruated
Causes of amenorrhoea?
Physiological - pregnancy, menopause
Primary - congenital problems e.g. Turners, Kallmann
Secondary - PCOS, POF, adhesions, weight loss, exercise, stress, high prolactin
Investigations for amenorrhoea?
LH, FSH, oestradiol, thyroid function, prolactin
US
Testosterone
Pituitary function tests + MRI
Karyotyping
Levels of FSH, LH and oestrogen in primary hypogonadism?
Problem with the ovaries
- high LH and FSH
- low oestrogen
Levels of FSH, LH and oestrogen in secondary hypogonadism?
Problem with hypothalamus or pituitary
- low LH and FSH
- low oestrogen
What is Premature Ovarian Failure?
Amenorrhoea, oestrogen deficiency and high FSH/LH occurring <40 years old as a result of loss of ovarian function
Possible causes of premature ovarian failure?
Chromosome abnormalities e.g. Turner’s syndrome, Fragile X syndrome
Gene mutations
Autoimmune e.g. Addison’s, thyroid
Iatrogenic - radiotherapy, chemotherapy
What can cause functional hypothalamic amenorrhoea?
Weight loss
Stress
Excessive exercise
What are the diagnostic criteria for PCOS?
- Menstrual irregularity
- Hyperandrogenism - hirsutism, acne, alopecia, high testosterone
- Polycystic ovaries on US
What is Turner’s syndrome?
XO karyotype
Congenital causes of primary hypogonadism in males?
Klinefelter’s syndrome
Acquired causes of primary hypogonadism in males?
Testicular trauma
Radiotherapy and chemotherapy
Varicocele
What is Klinefelter’s syndrome?
XXY - presence of an extra X chromosome in men
Testosterone, FSH and LH levels in primary hypogonadism?
low testosterone
high LH and FSH
Testosterone, FSH and LH levels in secondary hypogonadism?
low testosterone
low LH and FSH
