Table 1.

Examples of indications for genetic testing in endocrinology.

Indication	Clinical example	Informative result	Benefit of result
Differentiation or confirmation of clinical disorders	Mild, longstanding PTH-dependent hypercalcaemia and intermediate urinary calcium creatinine clearance ratio	CASR mutation	Diagnosis of familial hypocalciuric hypercalcaemia which does not necessitate treatment, rather than primary hyperparathyroidism which is treated surgically
Disease monitoring	Sporadic medullary thyroid cancer	RET mutation	Rationale for current and ongoing assessment for other MEN2-related tumours
Therapeutic guidance	Lean individual with longstanding diabetes mellitus, glycosuria and a positive family history of diabetes	HNF1A mutation	Confirmation of sulphonylurea-sensitive subtype of monogenic diabetes to facilitate safe and appropriate insulin withdrawal and replacement with a sulphonylurea
Prognostication	Lean individual with longstanding mild hyperglycaemia	GCK mutation	Diagnosis of GCK diabetes which is non-progressive and not associated with vascular complications, therefore not requiring treatment
Family testing primarily to guide surveillance	Clinical MEN1 syndrome	MEN1 mutation	Possibility of targeted mutation testing in presymptomatic at-risk family members to obviate the need for tumour surveillance in those who test negative
Family testing primarily to guide management	Clinical MEN2 syndrome	RET mutation	Possibility of targeted mutation testing in family members to facilitate prophylactic thyroidectomy
Family planning	Biochemically diagnosed non-classical congenital adrenal hyperplasia	One classic mutation and one variant allele in CYP21A2	Risk of classic congenital adrenal hyperplasia where the partner also carries a classic mutation in CYP21A2 may be overcome by IVF and preimplantation genetic diagnosis