Pituitary Flashcards
What is the hypophysis?
Another name for the pituitary gland
What is the neurohypophysis?
Another name for the posterior pituitary gland
What is the adenophysis?
Another name for the anterior pituitary gland
What is the infundibulum?
Another name for the pituitary stalk connecting the hypothalamus to the pituitary gland
Give two problems that pituitary pathology can cause on the surrounding structures
- Compression of the optic chiasm e.g. bitemporal hemianopia
- Compression of structures in the cavernous sinuses e.g. damage to cranial nerves III, IV,V1 (opth), V2 (max), VI
What are hypophysiotropic hormones?
Hormones which are released into the anterior pituitary gland to cause the release of anterior pituitary hormones
Name the 5 hypophysiotropic hormones and what they do
- Corticotrophin-releasing hormone (CRH) - Stimulates the release of ACTH
- Growth hormone-releasing hormone (GHRH) - Stimulates the release of GH but GHRH release is inhibited by somatostatin (SST)
- Thyrotropin-releasing hormone (TRH) - Stimulates the release of TSH
- Gonadotropin-releasing hormone (GnRH) - Stimulates the release of LH & FSH
- Dopamine (DA) - Inhibits the release of prolactin (PRL)
What does the abbreviation CRH stand for?
Corticotrophin-releasing hormone
What does the abbreviation ACTH stand for?
Adrenocorticotropic hormone
What does the abbreviation GHRH stand for?
Growth hormone-releasing hormone
What does the abbreviation GH stand for?
Growth hormone
What does the abbreviation SST stand for?
Somatostatin
What does the abbreviation TRH stand for?
Thyrotropin-releasing hormone
What does the abbreviation TSH stand for?
Thyroid stimulating hormone
What does the abbreviation GnRH stand for?
Gonadotropin-releasing hormone
What does the abbreviation LH stand for?
Luteinising hormone
What does the abbreviation FSH stand for?
Follicle stimulating hormone
What does the abbreviation DA stand for?
Dopamine
What does the abbreviation PRL stand for?
Prolactin
What type of hormones does the anterior pituitary produce?
Peptide hormones
Name the 6 hormones produced by the anterior pituitary and which cells produce them
- Follicle-stimulating hormone (FSH) - gonadotrophs
- Luteinizing hormone (LH) - gonadotrophs
- Adrenocorticotropic hormone (ACTH) (aka corticotropin) - cortiocotrophs
- Thyroid-stimulating hormone (TSH) (aka thyrotropin) - thyrotrophs
- Prolactin (PRL) - lactotrophs
- Growth hormone (GH) (aka somatotropin) - somatotrophs
Which hormone causes FSH and LH to be released from the anterior pituitary?
Gonadotropin-releasing hormone (GnRH)
Which organs do LH and FSH target?
The gonads
What does LH and FSH do in the ovaries?
- LH acts on the theca cells to convert cholesterol to testosterone
- FSH converts testosterone to oestrogen in the granulosa cell via the aromatase enzyme
What does LH and FSH do in the testes?
- LH acts on the Leydig cells to produce testosterone
* FSH acts on the Sertoli cells to initiate sperm production
What are the roles of oestrogen and progesterone in the control of FSH and LH?
- FSH stimulates oestrogen release
- Oestrogen inhibits FSH (+ve feedback) and causes a surge in LH
- LH causes the egg to release which stimulates the release of progesterone to thicken the uterine wall
Which hormones cause and inhibit the release of GH?
- Growth-hormone releasing hormone (GHRH) causes its release
* Growth-hormone inhibiting hormone aka somatostatin (GHIH/SST) inhibits release
State and describe the 3 actions of GH
- Increases blood glucose - stimulates gluconeogenesis and inhibits insulin
- Breaks down fat - works on adipose tissue
- Indirectly stimulates growth and protein synthesis - acts on the liver to increase protein synthesis and stimulate IGF-1 production
What does IGF-1 do and how is it related to GH?
- It acts on the skeleton to increase cartilage proliferation.
- It is stimulated by GH and it is the substance measured to reflect GH levels
Which hormone stimulates ACTH release?
Corticotrophin-releasing hormone (CRH)
Which organs does ACTH act on?
The adrenal glands
Which hormones does ACTH stimulate the release of and where from?
- Cortisol and other steroid hormones - zona fasciculata in the adrenal cortex
- Androgens - zona reticularis in the adrenal cortex
- Adrenaline - adrenal medulla
What are some of the major roles of cortisol?
- Regulates and breaks down proteins, fats and carbohydrates
- Has an anti-inflammatory effect – lowers immune response (but this can be bad if prolonged)
- Helps the body overcome stress
Which hormones cause and inhibit the release of TSH?
- Thyrotropin-releasing hormone (TRH) stimulates release
* Growth-hormone inhibiting hormone aka somatostatin (GHIH/SST) inhibits release
What does TSH stimulate the release of?
Thyroid hormones
Give some actions of the thyroid hormones
- Control rate of metabolic reactions
- Accelerate food metabolism
- Increase protein synthesis
- Stimulate carbohydrate metabolism
- Enhance fat metabolism
- Increases ventilation rate
- Increases cardiac output & heart rate
- Brain development during foetal life and postnatal development
- Growth rate acceleration
How does dopamine affect prolactin?
Dopamine inhibits prolactin
What is the action of prolactin?
Stimulates the breasts to produce milk and helps with breast development
What are the type of receptors that all pituitary and hypothalamic hormones act on?
G-protein coupled receptors
What does ADH stand for and what is another commonly used name for it?
Anti-diuretic hormone - aka vasopressin
Which hypothalamic neurones are responsible for oxytocin and vasopressin synthesis?
- Paraventricular nucleus - oxytocin synthesis
* Supraoptic nucleus - vasopressin synthesis
What are the names of the 2 hormones related to the posterior pituitary?
- Oxytocin
2. Vasopressin/ADH