The diagnosis of obesity is defined by a body mass index over 30 kilograms per metre squared.
Baseline investigations - all cases
Useful indicator of general health and underlying disease. Anaemia may exacerbate tiredness and breathlessness and so reduce exercise capacity.
Hypokalaemia may be present in Cushing's syndrome.
Useful indicator of general health and underlying disease. Fatty liver is common in obesity, diabetes and Cushing’s, though abnormal liver function should be investigated if indicated in the usual way. This is also needed as baseline before starting medical treatments.
Undiagnosed hyperparathyroidism may contribute to depression and tiredness and so exacerbate weight gain.
Untreated hypothyroidism is associated with weight gain and depressed mood.
Positive thyroid antibodies indicate an increased risk of future thyroid dysfunction and should trigger annual monitoring of TSH.
Essential to stratify and address other cardiovascular risk factors in all patients with possible metabolic syndrome.
Further investigations - selected cases only
Consider performing screening investigations for PCOS if clinically indicated. Where this is suspected clinically, diagnoses such as prolactinoma, hypothyroidism, virilising tumours, congenital adrenal hyperplasia and Cushing's syndrome must all be ruled out.