Neurohypophysial Disorders

Question 1

Describe the actions of the hormones released from the posterior pituitary and how they’re regulates

Answer 1

1. Vasopressin - acts on the renal corticol and medullary collecting ducts, stimulates synthesis and assembly of aquaporin and increased water transport, increased water reabsorption, antidiuretic effect on V2 receptor. It has other affects on V1a vasoconstrictor, V1b corticotrophin

Regulated: in the organum vasculosm, osmoreceotor (neurones) project to hypothalamic PVN and SON, trigger release. Osmoreceptors are very sensitive they enlarge and shrink.

2. Oxytocin

Question 2

Describe the effects, causes and treatment of diabetes insipidus

Answer 2

Causes of DI: 1. cranial: problem with production of VP, due to tumour etc 2. Nephrogenic: end-organ (kidneys) resistance to vasopressin (rare)

Symptoms: polyuria, hypo-osmolar, polydipsia, dehydration

Diagnostic via DDAVP, biochemical: hypernatraemia, raises urea, increased plasma osmolarity, dilute urine.

Treatment: V1 - terelipressin V2-desmopressin . Thiazides = inhibits Na+/cl- volume depletion and increased Na reabsorption and increases water retention.

Question 3

Describe the effects of Syndrome of Inappropriate ADH

Answer 3

Plasma vasopressin concentration is inappropriately high for the existing plasma osmolarity, increased vasopressin, increased H2O reabsorption from regal collecting duct, expansion of ECF volume > hyponatraemia.

Symptoms:

Causes: CNS (SAH, stroke, tumour), pulmonary disease, malignancy, drug-related, idiopathic

Treatment: surgery, fluid restriction, drug (demeclocyline), V2 antagonist