Differentials
Primary hyperparathyroidism
SIGNS / SYMPTOMS
No differentiating signs or symptoms.
INVESTIGATIONS
Hypercalcaemia associated with elevated parathyroid hormone level and normal or elevated 1,25-dihydroxyvitamin D level.
Hyperthyroidism
SIGNS / SYMPTOMS
Symptoms include weight loss, palpitations, anxiety, heat intolerance, hyperdefecation, tremor, diaphoresis.
Signs may include a goitre or palpable thyroid nodule(s); stare; lid lag; or exophthalmos (Graves' disease).
INVESTIGATIONS
Suppressed thyroid-stimulating hormone and elevated free T4 level.
Adrenal insufficiency
SIGNS / SYMPTOMS
Symptoms include fatigue, weight loss, anorexia, abdominal pain, muscle aches, lightheadedness, nausea, vomiting, and diarrhoea.
Signs may include orthostatic hypotension, hyperpigmentation of skin creases and buccal mucosa.
INVESTIGATIONS
Inadequate response to adrenocorticotrophic hormone stimulation.
Hyponatraemia.
Hypoglycaemia.
Phaeochromocytoma
SIGNS / SYMPTOMS
Symptoms include episodic headache, sweating, palpitations.
Signs include persistent hypertension, tachycardia.
INVESTIGATIONS
Elevated 24-hour urinary or plasma fractionated catecholamines and metanephrines.
Sarcoidosis
SIGNS / SYMPTOMS
Symptoms include cough, dyspnoea, chronic fatigue, arthralgia, wheezing, photophobia, painful red eye, blurred vision; may be asymptomatic; family history of sarcoidosis.
Signs include rhonchi, lymphadenopathy, erythema nodosum, lupus pernio, conjunctival nodules, facial palsy.
INVESTIGATIONS
Chest x-ray may show hilar and/or paratracheal adenopathy with upper lobe predominant bilateral infiltrates.
Serum ACE level may be elevated.
Medication-related hypercalcaemia
SIGNS / SYMPTOMS
History of use of thiazide diuretics, lithium, calcium supplementation, over-the-counter antacids, or large doses of vitamin D.
INVESTIGATIONS
Serum calcium slightly elevated and returns to normal after cessation of the medications.
Pulmonary tuberculosis
SIGNS / SYMPTOMS
Cough, fever, anorexia, weight loss, and malaise.
INVESTIGATIONS
Chest x-ray: primary disease commonly presents as middle and lower lung zone infiltrates. Ipsilateral adenopathy, atelectasis from airway compression, and pleural effusion can be seen. Reactivation-type (post-primary) pulmonary tuberculosis (TB) usually involves apical and/or posterior segment of right upper lobe, apicoposterior segment of left upper lobe, or superior segment of either lower lobe, with or without cavitation. As disease progresses it spreads to other segments/lobes.
Sputum smear: positive for acid-fast bacilli (AFB).
Extrapulmonary tuberculosis
SIGNS / SYMPTOMS
Enlarged lymph nodes, pleuritic chest pain, skeletal pain, headache, urinary symptoms, abdominal swelling or pain.
INVESTIGATIONS
Chest x-ray: evidence of unrecognised pulmonary TB or evidence of old healed TB (e.g. upper lobe fibrosis) may be present; pleural TB will usually have a small to moderate unilateral pleural effusion.
Sputum smear: positive for AFB.
Analysis of lymph node aspirate; pleural, cerebrospinal, or ascitic fluid; bone films; or urine may show evidence of TB infection.
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