Lecture 6 & 7: Pituitary Gland. Flashcards
1
Q
What are the main functions of the pituitary gland?
A
- Master gland of endocrine system
- Integrates signals from hypothalamus and secretes hormones and regulates the function of other endocrine glands
- Homeostasis
2
Q
Where is the pituitary gland located and what drives it?
A
- Small gland located at the base of brain below hypothalamus
- Hypothalamus drives the pituitary gland
3
Q
What are the 2 lobes called of the pituitary gland and what are their functions?
A
- Anterior: Synthesises and secretes hormones
- Posterior: Stores and secretes hormones
4
Q
What are the 2 hormones that the posterior pituitary gland stores and releases?
A
- ADH (Antidiuretic hormone)
- Oxytocin
5
Q
What are the main functions of ADH?
A
- Constriction of blood vessels
- Fluid reabsorption at kidneys
- Both increase the arterial blood pressure
6
Q
How does ADH cause blood vessel constriction?
A
- ADH binds to V1 receptors on smooth muscle which activates Gq signalling and increase calcium
- causes constriction and increases systemic vascular resistance -> increases BP
7
Q
How does ADH cause fluid reabsorption at kidneys?
A
- In response to dehydration
- ADH binds to V2 receptors in epithelial cells in collecting duct
- Activates GS signalling -> increases cAMP -> increases PKA -> phosphorylates aquaporin channels to move to CD
- Allow water reabsorption to blood
8
Q
What are some disorders related to reduced ADH?
A
- Diabetes insipidus: excessive thirst/ diluted urine. Can’t reabsorb water. (Dehydrated body)
- Copious hypotonic urine: excessive dilute urine
9
Q
What is the treatment for disorders relating to reduced ADH?
A
- Desmopressin (V2 agonist)
10
Q
What is the disorder related to too much ADH?
A
- Syndrome of inappropriate ADH (SIADH) : body produces too much ADH which causes water retention and low Na+
11
Q
What is SIADH caused by and what does it cause?
A
- It is caused by: trauma, head injury
- Causes: hyponatraemia & oedema
12
Q
What is the treatment when the body produces too much ADH?
A
- Demeclocycline: blocks transduction of V2: decreases kidneys response to ADH (cheap but doesn’t always work)
- Tolvaptan: V2 antagonist: increases water retention (expensive)
13
Q
What are the functions of oxytocin?
A
- Uterine contractions: binds to oxytocin receptors on uterus -> contractions which stimulates more oxytocin
- Milk ejection in breastfeeding: stimulates myoepithelial cells in mammary glands to contract & push milk when suckling
14
Q
What is the clinical relevance of oxytocin?
A
- Labour induction
- Prevent and treat haemorrhage (post partum - excessive bleeding after child birth)
15
Q
What is the name of the antagonist of oxytocin and what is it used for?
A
- Atosiban
- Used in pre term labour
16
Q
What are the hormones that the anterior lobe synthesises and secretes?
A
- Thyroid stimulating hormone (TSH)
- Adrenocorticotrophic Hormone (ACTH)
- Follicle Stimulating Hormone (FSH)
- Luteinising Hormone (LH)
- Growth Hormone (GH)
- Prolactin (PL)
17
Q
What controls/regulates the release of the 6 anterior pituitary hormones?
A
- Hormones from the hypothalamus aka Hypothalmic releasing factors
18
Q
What are trophic pituitary hormones?
A
- Thyroid stimulating hormone (TSH)
- Adrenocorticotrophic Hormone (ACTH)
- Follicle stimulating Hormone (FSH)
- Luteinising Hormone (LH)
19
Q
What are directly acting pituitary hormones?
A
- Growth Hormone
- Prolactin
20
Q
What is the releasing factor for Thyroid Stimulating Hormone (TSH)?
A
- Thyrotrophin/thyroid releasing hormone (TRH)
21
Q
What hormone is released by the the Thyroid Stimulating Hormone (TSH) and what does the hormone do?
A
- Thyroid hormone (T3 and T4) which regulates metabolism and growth
22
Q
What is the releasing factor for Adrenocorticotrophic Hormone (ACTH)
A
- Corticotrophin releasing hormone (CRH)
23
Q
What is released by the adrenocorticotrophic hormone and what does it do?
A
- Cortisol which goes into blood and regulates metabolism and other regulatory actions
24
Q
What is the releasing factor for LH and FSH?
A
- Gonadotrophin releasing hormone (GnRH)
25
Where does FSH work and what does it stimulate?
- Works in the gonads and stimulates ovarian follicle maturation in women and sperm maturation in men
26
What is released from the gonads as a result of FSH stimulation?
- Oestrogen/progesterone in women
- Testosterone in men
27
What does LH do in the Gonads?
- Induces ovulation and formation of corpus luteum
28
What is the releasing factor for growth hormone?
- Growth hormone releasing factor (GHRF)
29
What direct effects does the growth hormone have?
Direct effects
- Increased breakdown of triglycerides
- Increased protein synthesis
- Lactation
- Gluconeogenesis
30
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 involved in metabolic effects
31
What inhibits the release of GH?
- Growth Hormone releasing inhibiting factor (GHRIF) somatostatin
32
What are the growth promoting effects of IGFs
- In the bone it causes proliferation of epiphyseal cartilage
- It causes connective tissue proliferation
- Causes viscera hypertrophy/ hyperplasia
33
What syndrome occurs from a deficiency in GH secretion?
- Turners Syndrome
34
What syndrome occurs from GH receptor defects?
- Laron Type Dwarfism
- Failure to produce IGF in response to GH
35
How do we treat dwarfism due to GH secretion deficiency?
- Human growth hormone (recombinant)
- Somatotropins
- Must have GH deficiency and must improve QOL
36
What is the releasing factor for prolactin
- Prolactin releasing factor (PRF)
37
What tissues express prolactin (PL) receptors?
- Nearly all tissues express receptors
38
What effect does prolactin have on mammary tissue?
- Milk production
- Proliferation and differentiation of mammary tissue during pregnancy
39
What effect does prolactin have on gonadotrophin releasing hormones?
- Inhibits GnRH
- Prevents ovulation
40
What prevents the release of prolactin?
- Prolactin releasing Inhibiting factor (PRIF) (dopamine)
41
What are the symptoms of excess prolactin levels?
- Galactorrhoea/Gynaecomastia
- Infertility amenorrhea (absence of period)
- Osteoporosis
42
What causes excess amounts of prolactin?
- Tumour secreting PL or PRF
- Neuroleptics e.g. haloperidol (dopamine antagonist), metoclopramide, oestrogen
- Pregnancy, breastfeed, stress
43
What are the conditions caused by excess Growth hormone and treatment?
- Gigantism: excessive GH in early age. Rare. Results from pituitary tumour. Surgery
- Acromegaly: Excessive GH in adults. Bone and connective tissue. Surgery, radiotherapy or Bromocriptine (dop agonist), or GHRIF analogue (Octreotide)
44
What is hypopituitarism?
- Reduced secretion of all anterior pituitary hormones.
- Especially GH
45
What is panhypopituitarism and what are the causes?
- Deficiency of all anterior hormones
- Irradiation, Surgery, pituitary tumour
46
What does GH do with glucose?
- It counter regulates: hyperglycaemia, insulin resistance
- Insulin regulates IGF: Low insulin = bad regulation therefore poor growth in children w/ diabetes
- High prevalence of diabetes in GH disorders
