Adult Medical-Surgical Nursing Endocrine Module: Disorders of the Posterior Pituitary Gland

Hormones of the Posterior Pituitary  Anti-diuretic hormone (ADH)/Vasopressin:  Regulates the body’s water balance  Increased production when water must be conserved in the body  Promotes reabsorption of water by kidney tubules  Promotes vasoconstriction (BP)  Oxytocin: in pregnancy promotes labour and milk ejection postpartum

Disorders of the Posterior Pituitary  Diabetes Insipidus: hyposecretion of anti-diuretic hormone (ADH)  Syndrome of Inappropriate ADH (SIADH): hypersecretion of ADH from posterior pituitary gland or other tissues in the body

 Diabetes Insipidus:  Hyposecretion of anti-diuretic hormone (ADH)

Posterior Pituitary Hyposecretion: Diabetes Insipidus  Diabetes Insipidus is a condition of reduced secretion of Anti-diuretic hormone (ADH) or Vasopressin  Reduced ADH → increased urine output as water balance is not regulated

Diabetes Insipidus: Aetiology  Tumour (Pituitary adenoma especially chromophobic cells)  Trauma (head injury)  Post-craniotomy or post-irradiation of pituitary gland  Meningitis  Brain metastases  (May relate to ↓ renal response to ADH)

Diabetes Insipidus: Clinical Manifestations  High volumes of very dilute urine (SG – 1.005)  Dehydration and weight loss  Severe thirst especially for water ( ↑ plasma osmolality)  Hypotension and increased weak pulse

Diabetes Insipidus: Diagnosis  Fluid Deprivation Test: (continued production of dilute urine despite fluid deprivation, when the kidneys should normally conserve water)  Plasma levels of ADH, osmolality  Trial of Vasopressin to see effect  CT, MRI: to investigate cause if unknown

Diabetes Insipidus: Clinical Management  Treat the underlying cause  Largely increased fluid intake (IVI)  Manage electrolyte imbalance  Long-term HRT: Anti-diuretic hormone (Vasopressin, Desmopressin, Minirin)  Clofibrate: potentiates ADH if residual production of gland exists

Diabetes Insipidus: Nursing Considerations  Care in ICU:  Strict monitoring of urine output, vital signs, especially BP  Care of IV fluid and oral intake  Monitor urine specific gravity/ osmolality  Monitor blood electrolytes, osmolality  Patient education related to HRT

 Syndrome of Inappropriate Anti- diuretic Hormone (SIADH):  Hypersecretion from posterior pituitary gland or other tissues in the body

Posterior Pituitary Hypersecretion: Syndrome of Inappropriate ADH  Aetiology:  SIADH is often related to a bronchial or other malignant tumour in the body  Brain tumour  Trauma

SIADH: Pathophysiology  Bronchial or other tumour cells secrete ADH (or posterior pituitary cells if trauma)  Increased ADH levels →  Reduced urine output with very high concentration  Increased fluid retention with relative hyponatraemia (dilutional)

SIADH: Clinical Manifestations  Oliguria  Highly concentrated urine  Hypertension  Weight gain  Oedema  Symptoms of underlying cause

SIADH: Diagnosis  History and clinical picture  Blood hormone levels  Urine specific gravity  Serum electrolytes (sodium)

SIADH: Clinical Management  Treat the cause  Reduce fluid intake  Diuretics if necessary  If trauma may be self-limiting

SIADH: Nursing Considerations  Monitor BP, weight, urine output and concentration  Restrict fluid intake  Patient support and education