AVP, Oxytocin, Growth hormones and Pituitary Flashcards
what is the master gland of the endocrine system?
the pituitary gland
what does the pituitary gland do?
It integrates signals and releases hormones that regulate the function of other endocrine glands
what drives the pituitary gland?
the hypothalamus
what are the 2 parts of the pituitary gland called?
- posterior neurohypophysis
2. anterior adenohypophysis
what does the neurohypophysis do?
stores & secretes hormones synthesised in the hypothalamus e.g. oxytocin, ADH
what does the adenohypophysis do?
synthesises and secretes hormones in response to hypothalamic regulation e.g. TSH, ACTH, FSH, LH, GH, PL
what does the 2 hormones released by the posterior neurohypophysis regulate?
- ADH (antidiuretic hormone)/vasopressin = regulates renal function
- Oxytocin = regulates uterine contraction
how many peptides in the posterior pituitary hormones
9 amino acids
how does the posterior pituitary regulate renal function?
- Low blood pressure is detected by baroreceptors and high osmolarity is detected by osmoreceptors
- ADH is released from the pituitary in response
- V2 receptors in distal tubule of kidneys detect ADH and cause water reabsorption
- V1 receptors on smooth muscle also detect the ADH and cause vasoconstriction to increase blood pressure
what do we use to treat someone with too little ADH?
V2 agonists e.g. lypressin or desmopressin
what do we use to treat someone with too much ADH?
V2 antagonists e.g. demeclocycline or tolvaptan
how does the posterior pituitary regulate uterine contraction?
- Descent of foetus activates stretch receptors in uterus and high levels of oestrogen before birth increases oestrogen receptor number
- pituitary gland releases oxytocin
- uterus detects oxytocin causing uterine contraction (labour induction)
how does oxytocin control lactation?
- Suckling infant activates sensory receptors around nipples
- pituitary gland releases oxytocin
- Contraction of myoepithelial cells
(milk let down)
what are the 6 anterior adenohypophysis hormones?
- Thyroid stimulation H. (TSH)
- Adrenocorticotrophic H. (ACTH)
- Follicle stimulating H. (FSH)
- Lutenising H. (LH)
- Growth H (GH)
- Prolactin (PL)
what controls/regulates the release of the 6 anterior pituitary hormones?
hormones from the hypothalamus aka Hypothalamic releasing factors
what are the tropic pituitary hormones?
- Thyroid stimulation H. (TSH)
- Adrenocorticotrophic H. (ACTH)
- Follicle stimulating H. (FSH)
- Lutenising H. (LH)
what are the directly acting pituitary hormones?
- Growth H (GH)
2. Prolactin (PL)
what is the releasing factor for Thyroid stimulating hormone (TSH)?
Thyrotrophin releasing hormone (TRH)
what hormone is released by the Thyroid stimulating hormone (TSH) and what does the hormone do?
Thyroid hormone which regulates metabolism and growth
what is the releasing factor for Adrenocorticotrophic hormone (ACTH) ?
Corticotrophin releasing hormone (CRH)
what is released by the adrenocorticotrophic hormone and what does it do?
Corticosteroids which regulates Metabolism & other regulatory actions
what is the releasing factor for LH and FSH?
Gonadotrophin releasing hormone (GnRH)
where does FSH work and what does it stimulate?
works in the gonads and stimulates ovarian follicle maturation in women and supports sperm cell maturation in men.
what is released from the gonads as a result of FSH stimulation?
- oestrogen/progesterone for women
- testosterone for men
what does LH do to the gonads?
induces ovulation & formation of corpus luteum
what is the releasing factor for growth hormone?
Growth Hormone releasing factor (GHRF)
what effects does the growth hormone have?
Direct effects:
- increased breakdown of triglycerides
- increased protein synthesis
- Lactation
- gluconeogenesis
what is the effect of GH on the liver?
- causes the release of IGFs (insulin like growth factors) called ‘Somatomedins’
- Somatomedins stimulate bone growth, muscle growth, and are also involved in metabolic effects
what inhibits the release of GH?
Growth H. Releasing Inhibiting Factor (GHRIF) somatostatin
what are the growth promoting effects of IGFs?
-In the bone it causes proliferation of epiphyseal cartilage
-It causes connective tissue
proliferation
-It causes viscera hypertrophy/hyperplasia
what syndrome occurs from a deficiency in GH secretion?
Turners syndrome
what syndrome occurs from GH receptor defects?
Laron type Dwarfism
how do we treat dwarfism due to GH secretion deficiency?
- Human growth hormone (recombinant)
- GH extract from post-mortem pituitaries was used until shown to cause Creutzfeld-Jakob Disease.
what is the releasing factor for prolactin?
Prolactin releasing factor (PRF)
what tissues express prolactin (PL) receptors?
Nearly all tissues express PL receptors.
what effect does prolactin have on mammary tissue?
- Milk production
- proliferation & differentiation of mammary tissue during pregnancy
what effect does prolactin have on gonadotrophin releasing hormones?
Inhibits GnRH
prevents ovulation
what prevents the release of prolactin?
Prolactin releasing inhibiting Factor (PRIF) (dopamine)
what are the symptoms of excess prolactin levels?
- galactorrhoea/gynaecomastia
- Infertility amenorrhoea (absence of period)
what causes excess amounts of prolactin?
- Tumor secreting PL or PRF
2. Neuroleptics e.g. haloperidol (dopamine antagonist)
how do we combat excessive prolactin levels?
- Dopamine agonist e.g. bromocriptine
2. Surgery
