Diabetes insipidus
The inability to produce concentrated urine due to either antidiuretic hormone deficiency or resistance, which leads to extreme thirst and polyuria. The diagnosis may be confirmed using a water deprivation test.
General examination
To diagnose diabetes insipidus, a detailed and full general examination is mandatory in the initial assessment. The respiratory system should be examined in detail for signs of sarcoidosis, tuberculosis and other connective tissue diseases.
Blood pressure and volume status
A postural drop in BP indicates intravascular volume depletion. Skin turgor and mucous membranes should also be assessed.
Ear, nose and throat examination
Signs of Wegener's granulomatosis should be sought.
Breast or testicular examination
This should be performed in all patients due to the possibility of metastatic disease or germ cell tumours.
Thyroid
The thyroid gland should be examined in all patients presenting with possible metastatic disease.
Musculoskeletal system
The joints should be examined in detail for signs of connective tissue disease.
Muscle wasting may occur in glucocorticoid deficiency.
Proximal myopathy may occur in hypokalaemia or hypothyroidism and slow relaxing reflexes may occur with loss of thyroid function.
Digital rectal examination
Consider performing this in all patients presenting with apparently isolated DI in case of metastatic disease.
Pituitary status
Visual acuity and visual fields
Full assessment of acuity and fields is mandatory in all patients suspected of DI to detect chiasmal compression or other involvement of the optic pathways.
Visual fundoscopy
Disc pallor is indicative of long-term visual loss which may not recover after decompression of the optic pathway.
Papilloedema is an indicator of raised intracranial pressure requiring urgent investigation.
Cranial nerves III-XII
Full cranial nerve assessment is important in all patients with suspected peri-pituitary tumours.
The nerves of the cavernous sinus are most frequently affected, though a VI nerve palsy may be a false localising sign associated with increased intracranial pressure.
Skin
Turgor is assessed by pinching the skin of the back of the hand and observing how quickly the skin resumes its usual character.
Fine wrinkling of the skin occurs in hypopituitarism.
Pallor may also occur with a normocytic normochromic anaemia with glucocorticoid deficiency.
Doughy pallid 'myxoedematous' skin may be seen with loss of thyroid function.
Thyroid status
Specifically seek signs of thyroid dysfunction.