Hypothalamus and Pituitary ☺️

Question 1

Describe the basic structure of the HP axis

Answer 1

Hypothalamus - SO, PV
-nuclei release releasing hormones into portal circulation => AP
Endocrine cells release trophic hormones into hypophyseal circulation => systemic circulation

Neural axons from hypothalamus release ADH, oxytocin directly into hypophyseal circulation in PP => systemic circulation

Pituitary in sella turcica in sphenoid
Pituitary next to optic chiasm

Question 2

Female hormone negative feedback system

Male hormone negative feedback system

Answer 2

Hypothalamus GnRH => AP gonadotrophs
FSH => follicle dev => O, inhibin
LH => ovulation => corpus luteum => P

FSH => Sertoli cells (spermatogenesis) => Inhibin
LH => Leydig cells => T
Leydig stimulate Sertoli

Question 3

GH

• function
• source
• regulation and release pattern

Answer 3

GHRH => somatotroph (most abundant cell in AP) => GH
Somatostatin => somatotroph => somatotropin => GH inhibition

Function

• growth of long bones until epiphyses fuse
• increase visceral size
• gluconeogenesis, lipolysis, protein synthesis
• cell growth
• stimulates IGF release from liver

Increases secretion

• pulsatile GHRH
• fasting (post prandial/drug induced hypoglycemia)
• exercise (tissue repair/AA infusion)
• sleep

Decreases secretion

• glucose
• somatostatin (increased by IGF)

Question 4

PRL

• function
• release

Hyperprolactinemia

• risk factors
• presentation in men, women
• management

Answer 4

TRH => lactotrophs => PRL stimulation
Dopamine => lactotrophs => PRL inhibition
PRL inhibits GnRH

• breast dev in pregnancy
• milk prod postpartum

Female, childbearing age, MEN 1

Men - impotence, low libido, galactorrhea, gynecomastia
Women - amenorrhea, galactorrhea

D2 agonists - bromocriptine/cabergoline

Question 5

Excess GH

• causes
• presentation
• management

Answer 5

Gigantism - hyperactive pituitary tumour, increased bone length before epiphyseal fusion

Acromegaly - hyperactive pituitary adenoma/ectopic GHRH/GH prod after epiphyseal fusion => loss of normal pulsatile release

• coarse facial features, spade hands, increased shoe size
• large tongue, interdental spaces
• sweat gland hypertrophy

Transphenoidal surgery - adenoma removal

Somatostatin analogues - octreotride/lanretide/pasireotide

D2 agonists - bromocriptine/cabergoline

Question 6

Insufficient GH

• presentation
• management

Answer 6

Dwarfism
GH deficiency after epiphyseal fusion

Before epipheaseal fusion
-recombinant hGH/hIGF -somatropin/mecasemin

Question 7

PP hormones

• release and regulation
• functions

Answer 7

SO, PV nuclei
ADH - hyperosmolarity
-ANG2, SNS => VC, fluid uptake

OXY - uterine contracts, milk ejection, social behaviour
-labour, lactation

Question 8

What are the 4 types of hormone deficiency

Answer 8

Resistance
-target hormone receptor faulty

Primary
-endocrine gland cannot release target hormone

Secondary
-Pituitary can’t release trophic hormone

Tertiary
-Hypothalamus can’t release releasing hormones

Question 9

What are the 2 key principles of hormone replacement

Answer 9

Replace the hormones that are required

Recognize diurnal patterns of release

Question 10

Pituitary adenomas

• different presentations
• investigations
• management

Answer 10

Functional adenoma => hyperpituitarism
Non functional adenoma => hypopituitarism if it gets big enough
-low TSH => fatigue, weight gain
-low FSH, LH => decreased libido, menses
-low ACTH => thin hair, skin

Both lead to mass lesion

• bitemporal hemianopia => optic chiasm compressed
• headache => increased pressure
• hypopituitarism => pituitary compressed

Apoplexy => hypopituitary

CT =>suprasella mass
Hyper/hypo => measure trophic and target hormone
Insulin stress test to test pituitary response to hypoglycemia => normally GH, cortisol increases

Benign - watch and wait
Transphenoidal surgery, endocrine replacement
Radiotherapy
Inhibiting hormones for hyperactivity