Typically the endocrinologist is presented with a severely ill patient in whom there is no prior history suggestive of pituitary disease, in whom clinical findings of hypothyroidism are either absent or masked by other disorders, with a T4 and FTI (by an index method) that are low, a low or normal TSH, and , if measured, a low T3. If T4 is below 4 ug/dl in this setting the diagnosis of NTIS, associated with a potentially fatal outcome, may be assumed. RT3 may be normal or elevated, and is not diagnostic. An elevated TSH suggests the presence of prior hypothyroidism, which should be treated. Finding positive antithyroid antibody titers supports the diagnosis of primary hypothyroidism, but does not prove it.

Serum cortisol should be measured. Transient apparently central hypoadrenalism is an unusual but well recognized phenomenon is severe illness( 114-116). Cortisol should be above 20 ug/dl, and commonly is above 30. If below 20, ACTH should be drawn and the patient should be given supportive cortisol therapy. Serum cortisol should certainly be determined if thyroid hormone is to be given. Since CBG may be reduced, it is advisable to measure serum free cortisol if possible. It is useful to determine FSH in post-menopausal women as a sign of pituitary function, but this is less clearly valuable in men. If there is a reason to consider hypopituitarism, a CAT scan of the pituitary is appropriate, or at least a skull film.

Aspirin, dilantin and carbamazepine can lower T4 and FTI as measured by several "Index" methods, Dopamine used in the setting of severe illness can induce clear-cut hypothyroidism. Hyperthyroidism is the typical cause of suppression of TSH below 0.1uU/ml, but is rarely difficult to exclude this diagnosis in the setting of severely depressed T4 and T3.