Indications: Historically, the TRH test was important in defining subtle degrees of Hypo- and Hyperthyroidism. With the advent of high sensitivity TSH measurements and redefined robust assays for FT3 and FT4 the role of the TRH test is limited.
As part of Combined Anterior Pituitary Function Testing in the work-up of hypothalamic pituitary lesions.
Rarely, to aid in diagnosis of a TSH secreting tumour (TSH-oma)
Avoid in early pregnancy
Transient pressor effects, variations in blood pressure and tachycardia can occur. Best avoided in those with coronary artery disease, hypertension, obstructive airways disease or asthma. TRH has been implicated as a cause of pituitary apoplexy in patients with pituitary adenomas.
Transient nausea, metallic taste, desire to micturate, flushing and elevation of systolic and diastolic blood pressure.
Withdraw Thyroid hormone replacement treatment one month prior to testing.
Otherwise, no special patient preparation required. No requirement for fasting.