Pituitary gland and disorders Flashcards
Where does the pituitary sit?
In the mid cranial fossa in the sella turcica of the sphenoid bone
What is the pituitary gland directly attached to? How does this happen through what membrane does this happen?
Pituitary is connected. hypothalamus via the infundibulum which pierces through the diaphragma sellae into the sella turcia
What axis does the pituitary form?
Hypothamo-pituitary axis
What is the anterior pituitary also known as
The adenohypophysis
What does the adenohypophysis comprise of?
Pars distalis
Pars intermediate
and the pars tuberalis that wraps around the pituitary stalk
What is the pars distalis?
contains glandular endothelial cells that produce anterior pituitary hormones as well as a rich fenestrated capillary network supported by fibroblasts and reticular fibres
What does the neruohypophysis or posterior pituitary comprise of?
Infundibular stalk and infundibular process that forms the posterior lobe
Is an extension of the hypothalamus therefore is neural tissue
What does the posterior pituitary contain?
What hormones does it produce?
Axons of neurones that originate in the supraoptic (mainly AVP) nuclei and the paraventricular (mainly oxytocin) nuclei of the hypothalamus
axons pass down the supraopticohypophyseal tract into capillary bed where they secrete oxytocin and vasopressin (ADH) via neruosecretion
Chromaphils are the secretory cells in the anterior pituitary what are the subtypes
Acidophils pink staining
basophils more blue staining
What cells are the acidophils in the anterior pituitary?
What is their histological apperance?
Somatotrophs
very large nuclei most numerous cell in the anterior pituitary produce and secrete GH which is packed in many vehicles in the cytosol
Lacto-mommotropic cells produce prolactin
What are the basophils that are present in the anterior pituitary?
Gonadatropic cells
produce LH and FSH
large cells with large nuclei
Corticotropic cells
produce ACTH
sparser secretory granules vesicles located on periphery
Thyrotropic cells
produce TSH
smaller granule contain vesicles located on the periphery
What are the two main blood vessels that bring blood to the pituitary gland?
Where do they stem form?
What part of the pituitary do they supply
Superior hypophyseal arteries stem from internal carotid artery bring blood to the median eminence of the hypothalamus and the infundibular stalk
Inferior hypophyseal artery that supplies the posterior pituitary
What is significant about the superior hypophyseal artery?
Blood supply to median eminence of the hypothalamus capillaries then region into blood sinusoids down into the pars distalis then branches to form an extensive capillary network
This is known as the hypothalamicHypophyseal portal system and allows hormones produced by the pituitary to reach the anterior pituitary without entering systemic circulation
What is the venous drainage of the pituitary gland
The hypophyseal vein
What is significant about the pituitary glands location?
Superior is the optic chiasm
surrounded laterally anteriorly and posteriorly by the cavernous sinus
and surrounded inferiorly by the sphenoid sinus
What is significant about the cavernous sinus and the pituitary gland
Contains cranial nerves III, IV, VI and V1 and V2 in order from superior to inferior
as well as the internal carotid artery
as such there is a lot to avoid when carrying out pituitary surgery
What are tropic hormones
hormones that target other endocrine tissues
What are the tropic hormones produced by the pituitary?
FSH
LH
ACTH
TSH
What are the other non-tropic hormones produced by the anterior pituitary
Prolactin
Growth hormone
What stimulates growth hormone secretion?
GHRH growth hormone releasing hormone produce by the hypothalamus
Also stimulated by sleep hypoglycaemia and exercise
What is the function of GH, and how does it carry out this role?
Cell division
protein synthesis
glucose metabolism
bone growth
It does this indirectly through the production of insulin growth factor one (IGF-1) in the liver which then triggers the mitogenic and metabolic effects of the GH
What inhibits GH
high GH levels and high IGF-1
hyperglycaemia
somatostatin
What does GH deficiency result in
Stunted growth and delayed development results in dwarfism in children
decreases muscle strength and exercise capacity
decreases bone mineral density
How is GH deficiency diagnosed? What test do you do?
Secretion of GH naturally pulsative higher at night
Growth hormone stimulation tests given insulin that results in hypoglycaemia should result in an increase in GH secretion
IGF-1 levels also measured
What is GH excess?
What causes this?
What does it cause and what are the symptoms of this disease?
Leads to acromegaly or gigantisism in children
Caused by a pituitary adenoma
no reduction or natural drops in GH levels
Acromegaly: growth of facial skeleton protruded jaw growth of hands and feet issues with fertility and heart thickened skin difficulty sleeping inter dental spacing
What are the local effects of pituitary adenomas
headaches
pressure on the optic chiasm resulting in visual field loss bitemporal hemianopia
lateral expansion can lead to compression of cranial nerves in cavernous sinus
Treatment of GH excess?
Surgery to remove pituitary adenoma
transsphenoidal surgery
Radiotherapy
somatostatin analogues can be given as long actin preparations
LH and FSH
What simulates production?
What is the role of FSH and LH?
Produced by gonadtropic cells
Stimulated to produce LH and FSH by GnRH gonadatropin releasing hormone
FSH and LH Peptide hormones with an inactive A subunit and specific B subunit that is activated once cleaved
Role in the development of secondary sex characteristics
production of sex hormones oestrogen and testosterone
What inhibits FSH LH
high GnRH
high FSH
high LH
and various other sex hormones
FSH LH deficiency?
Effects?
Treatment?
Leads to delayed puberty in children and poor development of secondary sex characteristics
Leads to decreased fertility and libido in women and osteoporosis
leads to decreased libido and infertility in men as well as loss of muscle mass
Treatment:
FSH and LH replacement therapy
FSH LH excess
VERY RARE
FSHomas of pituitary
will lead to menstural irregularities as well as enlarged testicles
Treatment is surgery
ACTH what does it stand for?
Adrenocorticotropic hormone
What stimulates ACTH release and what is its role?
Stimulated by release of CRH (corticotropin releasing hormone) by the hypothalamus
Also stimulated by stress
controls cortisol production by the adrenal glands which itself has a key role regulating the production of other steroids produced by the adrenal gland
What inhibits ACTH
high ACTH
high CRH
high levels of many other hormones it results in the production of
ACTH excess?
results in Cushings disease
central obesity moon face thick skin striae on skin easy bruising osteoporosis
Diagnosis
Treatment of ACTH excess?
high cortisol leaves loss of diurnal rhythm no significant drop in cortisol level
Transsphenoidal surgery to remove pituitary adenoma
TSH
Stimulation
Role
Inhibition
Produced by thyrotropic cells
Stimulated by TRH Thyrotropin releasing hormone
Role in thyroid gland and thyroid home regulation
Inhibited by high TSH high thyroid hormone levels
TSH excess due to pituitary adenoma
Hyperthyroidism
TSH-omas VERY RARE cause
Treatment is transsphenoidal surgery
TSH defficency
secondary Hypothyroidism
Prolactin
Produced by lacto-/ mammotropic cells
stimulated by breast feeding and pregnancy
allows mammotropic glands to produce milk following childbirth and inhibits gonadal activity through inhibition of GnRH
Hypothalamus inhibits PRL release via dopamine
Prolactin excess?
Cause?
Symptoms?
When no pregnant can be caused by drugs (dopamine antagonists) or through pituitary adenomas
Galactorrhoea milky nipple discharge and hypogonadism
Treatment dopamine agonists to degrease PRL levels and the size of the tumour
ADH or vasopressin AVP?
Role?
Produced and released by neurosecretory cells in the posterior pituitary
Increases the rate of free water reabsorption in the luminal membrane of kidney through V2 receptors causing integration of aquaporins into luminal membrane of collecting duct
Stimulated by hyperosmoregularity of the circulate effective circulating volume
What is AVP deficiency Causes how is it diagnosed? treatment?
Diabetes insipidus
Autoimmune destruction of neurosecretory cells tumors trauma infection inheritance
have to determine it is not diabetes mellitus measure blood gluc
Water deprivation test urine output should decrease in people who are normal will remain the same for ADH deficiency
Treatment ADH analogues
What is inadequate production of pituitary hormones called?
What is inadequate production of hormones from the anterior pituitary called?
hypopituitarism
Panhypopituitarism
Give three causes of hypopituitarism
Trauma to the pituitary
non functional Pituitary adenomas
Pituitary infarction
Causes of hyperpituitarism
functional pituitary adenomas
hypothalamic disease rare
ectopic production of hypothalamic agents
