Anterior Pituitary Flashcards
What is the hypothalamus-pituitary axis?
a hub of feedback loops that maintain homeostasis
How does the hypothalamus regulate the anterior pituitary gland?
- hypothalamus receives neural stimuli and generates chemical signals that signal to the pituitary
- hypothalamic releasing and inhibiting hormones are carried in the hypophyseal portal vessels, to the anterior pituitary, where they regulate the release of anterior pituitary hormones
What do the non-hypothalamo-hypophyseal outputs affect?
hunger, thirst and sexual behaviour
Where do the hypothalamic hormones travel through?
in the hypophyseal portal vessels to the anterior pituitary
Describe the importance of the arrangement between the hypothalamus and the pituitary gland?
- it allows intricate regulation of hormones levels
2. it amplifies the initial signal so that the few neurons can affect cells throughout the body
Describe the secretion of hormones of the hypothalamus?
- very small quantities of hormones
2. released in a pulsatile manner - the pulses vary in amplitude and rate, often with a circadian rhythm
Describe the structure of the hormones excreted by the hypothalamus?
small peptides (between 3 & 44 AA residues) - except for dopamine which is derived from the AA tyrosine
How do these hormones act?
they act on secretory cells in an excitatory (e.g. TRH) or inhibitory (e.g. GHIH) manner
What are the target cells in the anterior pituitary gland for gonadotrophin-releasing hormone?
gonadotrophs
What is the effect of GnRH on the anterior pituitary?
increase luteinizing hormones + follicle stimulating hormone release
Target cells for Thyrotrophin-releasing hormone?
thyrotrophs + lactotrophs
What is the effect of TRH on the anterior pituitary?
increase TSH and prolactin release
Target cells for prolactin-releasing factors?
lactotrophs
Effect?
increase in prolactin release
Target cells for dopamine? (prolactin inhibiting hormone)
lactotrophs
Effect?
decrease in prolactin release
Describe the structure of hormones secreted by the anterior pituitary?
large peptides (about 200 AA residues) or glycopeptides
Name the 6 main hormones of the anterior pituitary?
- growth hormone (GH) 2. thyroid stimulating hormone (TSH/thyrotrophin) 3. adrenocorticotrophic hormone (ACTH) 4. luteinizing (LH) 5. follicle stimulating hormone (FSH) 6. prolactin (PRL)
Describe how these hormones are stimulated, inhibited, their target organ and their effect?
Study table on slide 15-16
These hormones act in what 2 ways?
- regulation of other endocrine organs - TSH, ACTH, GH, LH, FSH 2. direct effect on distal organs - prolactin
Describe tumours of the anterior pituitary?
tumours of the secretory cells - adenomas
Diseases of the anterior pituitary are a result of which 3 processes?
- hyperpituitarism 2. hypopituitarism 3. Compression of surrounding structures – caused by space-occupying lesions
Growth hormone deficiency causes?
- dwarfism in children and adults 2. GH deficiency sydrome
Excess growth hormones causes?
- gigantism in children 2. acromegaly in adults
