Endocrinology: Hypothalamus and Pituitary Gland Flashcards
Describe the location of the pituitary gland
Protrudes from base of hypothalamus, sits in the sella turcica, close proximity to the optic chiasm.
What happens to the pituitary gland in pregnancy.
Becomes larger
Which hormones are secreted by the hypothalamus?
Thyrotrophin releasing hormone TRH Corticotrophin releasing hormone CRH Somatostatin Growth Hormone releasing hormone GHRH Dopamine
What is the embrological origins of the anterior and posterior lobes of the pituitary gland
Anterior lobe: Ectodermal cells of the oropharynx in the primitive gut
Posterior lobe: Neural crest cells
What is 3 elements that regulate the anterior pituitary gland
Hypothalamic input
Feedback from hormones
Paracrine and autocrine secretions of the pituitary gland
What hormones do the anterior pituitary gland produce?
Growth Hormone GH Thyroid stimulating hormone (TSH) ACTH FSH LH Prolactin
What inhibits GH secretion
IGF I - negative feedback
Somatostatic from hypothalamus
What increases GH secretion
What increases sensitivity of GH
GHRH
Estadiol
How many pulses of GH secretion a day during adulthood
5
GH is produced by what cell, what % of the total cells of the anterior pituitary gland
Somatotophs
40-50%
Prolactin is produced by which cells? What % of total cells
Lactotrophs
10-15%
What are the effects of prolactin
Important in lactation, other roles not clear.
Prolactin levels of non-lactating female same as men
Prolactin receptors on many tissues
Want is the overall effect of hypothalamus hormones on prolactin production?
Most inhibitory (different to all other ant pituitary hormones) - somatostatin and dopamine
Prolactin also has negative feedback
What stimulation prolactin
Suckling TRH Pregnancy Ostrogen Dopamine D2 receptor antagonist Sleep & stress
What cells make gonadatophins? What % of cells
Gonadotroph
10-15%
Where does LH bind in the testes/ovaries
Testes: Leydig cells
Ovaries: Theca/granulosa cells
Where does FSH bind in the testes/ovaries
Testes: Granulosa cells
Ovaries: Theca/granulosa cells
What hormones are produced from the posterior pituitary gland?
Arginine vasopressin
Oxytocinin
What is the effect of vasopressin in the kidney?
Binds to DCT & collecting ducts, adds aquaporins.
Increased H20 reabsorption and therefore decreased osmolality
What stimulated the release of vasopression
Increased osmolality Decreased BP N+V Stress Exercise
What drinks release of vasopressin
Caffeine
ETOH
Where is oxytocin produce
Posterior pituitary
Hypothalaus
Peripheral tissue (uterus, plancenta, corpus lute, testies, heart)
What are the effects of oxytocin
Lactation
Uterine contraction
What hormonal change are seen at onset of puberty?
Increased GnRH production and therefore increased LH and FSH production.
During puberty nocturnal rhythm with rise in LH overnight. This is lost in adulthood.
These stimulate the gonads to release sex steroids and induce physical changes.
What are the easiest signs of puberty in males and females?
Males: Tesitcular growth
Females: Breast development
When does mensus start?
When ostrogen has stimulated the growth of the uterus enough so that the withdrawal of the hormones cause first mensus
What hormones stimulate hair growth?
Gonadal steroids & adrenal steroids
What is considered precocious puberty in males & females?
Males < 9 yrs
Females < 8 years