The anterior lobe of the pituitary gland Flashcards
Where/How are hormones released from the anterior lobe of the pituitary gland?
Hormones are released into a local portal circulation system that perfuses the anterior pituitary - called the hypophyseal portal system
What are the** 5 endocrine cell types** of the anterior lobe & what trophic hormones do they release?
- Corticotrophs - ACTH
- Gonadotrophs -FSH and LH
- Thyrotrophs - TSH
- Lactotrophs - Prolactin
- Somatotrophs - GH
Which 2 of the 5 endocrine cells are acidophils? (based on staining properties)
- Somatotrophs
- Lactotrophs
Which 3 of the 5 endocrine cells are Basophils? (based on staining properties)
gonadotrophs
corticotrophs
thryotrophs
Which of the 5 endocrine cells are Basophils?
- Thyrotrophs
- gonadotrophs
- corticotrophs
What is hypopituitarism?
- anterior pitutary dysfunction - short supply of one of the anterior pituitary hormones
Give an example of hypopituitarism ( ie gene mutation & what hormones are affected?) IN A MOUSE
- recessive PIT1 mutation
- a decrease in prolactin & GH & TSH
What hormone does corticotropic releasing hormone cause production of?
adeno cortico tropic hormone (ACTH) which acts on the adrenal glands
What 2 hormones does GnRH cause the production of?
- Follice stimulating hormone
- lutinising hormone
What hypophysiotrophic hormone causes the production of GH and what is it’s target?
GHRH
* targets are liver, bone, skeletal muscle
Which one of the anterior pituitary hormones is not a peptide hormone or trophic hormone?
Prolactin
What is prolactin release** inhibited** by?
dopamine
What is prolactin release stimuated by?
- estrogen / progesterone
what are the physioogical roles of prolactin?
primary and secondary roles
- lactation - primary
- immune tolerance? - secondary
- behvaioural role - ie nuturing instinct
What does prolactin stimulate during pregnancy?
- it stimulates the development of the breast as a glandular tissue
- it promotes lobuloalveolar proliferation and development in the latter half of pregnancy
what is mammogenesis?
- the development of a functional breast
Describe the development of a breast
- breast development begins in puberty due to increased estrogen and progesterone levels
- development is completed in third trimester of pregnancy in reponse to sustained high levels of these hormones as well as prolactin
what is hyperprolactinemia, what can it stimulate and what are the consequences in some women?
- excessive levels of prolactin in the blood
- stimulates lactation
- in some women, it can cause amenorrhea (absence of menstrual cycle)
Describe the sucking reflex that stimulates the** production of prolactin**
- sucking stimulates the mechanoreceptors on the nipple
- this decreases dopamine secretion (which naturally inhibits prolactin)
- therefore anterior pituitary secretes prolactin
- increase in plasma prolactin levels
- stimulates gland cell and milk synthesis
what is galactorrhea?
milk secretion from non pregnant woman
what does the anterior lobe of the pituitary gland develop from?
- comes from the ectoderm - it moves upwards to join the infundibulum from the hypothalamus
Because the anterior pituitary gland moves upwards during development, what can be a problem in the future?
- there is a possibility of small clusters of epithelial cells being left behind along the path and these may develop into cysts or **ectopic hormone secreting tumours **later in life
what depression of the sphenoid bone does the anterior lobe sit in?
- the sella turcica which is covered by the diaphragma sellae
what does the pituitary gland lie directly beneath & as a result of a tumour what can happen?
- the **optic chiasm **
- any** increase in mass** eg a tumour can cause the pituitary to bulge upwards and press on the optic chiasm which may cause visual disturbances
