SDL 4: diseases of posterior pituitary

central diabetes inspidus or idiopathic diabetes insipidus

hypothalamic diabetes insipidus is aka

gestational diabetes insipidus

type diabetes insipidus caused by accelerated metabolism of vasopressin

antibodies directed against magnocellular neurons

typical cause of idiopathic diabetes insipidus

idiopathic hypothalamic diabetes insipidus

-histology shows lymphocytic inflammation of the pituitary stalk and posterior pituritary

thickening or enlargement of pit. stalk or post pit

MRI findings of idiopathic diabetes insipidus

autosomal dominant mutation of AVP gene

inheritance of familial hypothalamic DI

craniopharyngiomas and primary germ cell tumors

-lymphomas, leukemias

tumors that are characteristically associated with DI

sarcoidosis, tuberculosis, langerhans cell histiocytosis

granulomatous diseases associated with DI

vasopressinase

this enzyme rises late in pregnancy and degrades ADH, causing gestational DI

-X linked recessive mutation in AVPR2 gene, which encodes V2 receptor

-less common: AD or AR mutation of AQP2 gene

inheritance of hereditary nephrogenic diabetes insipidus

lithium drugs

acquired nephrogenic diabetes insipidus is caused by

polyuria and polydipsia

predominant symptoms oof diabetes insipidus

-severe hypernatremia with devastating effects on CNS---> hypertonic encephalopathy (brain shrinkage, obtundationo, coma, seizures)

complication of diabetes inssipidus

1) polyuric phase via inhibition of vassopressisn

2) antidiuretic phase due to release of stored hormones

3) permanent DI when stores of vasopressin are exhausted

triphasic clinical presentation of DI resulting from head trauma

the 24-hour urine osmolality is <200 mOsm/L. The average normal 24-hour urine osmolality is 500-800 mOsm/kg

urine osmolality in pt with DI

-dehydration phase: no oral intake fromo 10PM to 6AM; measure osmolarity/weight

-desmsopressin phase (administer and measure)

what are the three phases of the water deprivation test to determine cause of DI?

similar to that of normal pts

water deprivation test findings in pts with primary polydipsia

-psychogenic and dipsogenic

what are the two types of primary polydipsia?

Dispogenic polydipsia

includes patients with an increased sensation of thirst due to hypothalamic lesions (inflammation, infiltration, and infection) and subjects with habitual polydipsia, which is typically seen in life-style conscious men and women, which is the use of water to detox the body.

stress induced increases in dopamine levels stimulatless thirst centers

suggested pathogenesis of psychogenic polydipsia

manifest as nausea, vomiting, delirium, ataxia, seizures, and coma, and may even be fatal

presentation of water intoxication

Desmopressin

tx for central diabetes insipidus

renal absorption of excessive amounts of free water, hyponatremia and plasma hypo-osmolality.

-concentrated urine and reduced urine volume

effect of SIADH

SIADH

most frequent cause of hyponatremia in the hospital setting

-secretion of ectopic ADH by malignant neoplasm

-excessive ADH from posterior pituitary in meningitis, encephalitis, abscess stroke, neurosurugery

-drug induced

most frequent causes of SIADH

meningitis, encephalitis, brain abscess, stroke, intracranial bleeding, and neurosurgery

diseases that can cause excessive ADH secretion

ANP

-increases urinary sodium excretion; reduces hypervolemia but aggravates hyponatremiia

compensatory increases in ______ hormone with SIADH

vasopressin esscape

-mechanism in SIADH whereby water excretion will increase over time with decrease in urine osmolality

-helps keep urine lesss concentrated

-most pts are asymptomatic

-weight gain

-edema clinically undetectable

-ccellular swelling and brain edema due to hyponatremia

presentation of SIADH

gastrointestinal manifestations such as anorexia, nausea, and vomiting; and (ii) neuropsychiatric manifestations such as headaches, blurred vision, lethargy, apathy, disorientation, agitation, irritability, and seizures.

symptoms of SIADH

hyponatremia (serum sodium under 135)

-high urine sodium

-BUN <10

defining feature of SIADH

complete recovery when agent withdrawn

prognosis of drug induced SIADH

permanent neurologic impairment from central pontine myelinolysis

complication of rapidly correcting sodium

Craniopharyngioma

rare extra-axial epithelial tumor the sellar region

adamantinomatous and papilllary

histological types of craniopharyngioma

CTNNB1 mutation resulting in accumulation of B-catenin

gene associated with adamantinoomatous craniopharyngnioma

B-catenin accumulation

-immunohistochemical sign of cranyiopharyngnioma

functions in cell adhesion and as a downstream transcriptional activator in the Wnt signaling pathway

function of B-catenin protein

activating BRAF V600E mutation; component in MAPK signaling pathway

mutation associated with papillary craniopharyngiomas

Adamantinomatous craniopharyngioma

CPH tumor type that occurs mostly in children

lobulated spongy mass that usually contains cystic spaces

gross pathology of Adamantinomatous craniopharyngioma

Adamantinomatous craniopharyngioma

what type of CPH?

-nests of stratified squamouss epithelim

-top layer forms wet keratin which is heavily calcified

-basal layer

-inermediate layerr of reticulum

-top layer--> wet keratin

layers of the nests in Adamantinomatous craniopharyngioma

Papillary craniopharyngioma

CPH with fibrovasculuar core covered by mature squamous epithelium

craniopharyngeal canal; remnant of rathke's pouch

where do CPH tumorss arise

increased IICP, compression of optic chiasm, symptoms of hypopituitarism

clinical presentation of CPH

Adamantinomatous CPHs typically have a lobulated contour as a result of usually being multiple cystic lesions. Papillary CPHs tend to be more spherical in outline

Adamantinomatous craniopharyngioma vs papillarry on MRI

CT or MRI

imaging of choice for CPHs