Introduction and definition
	Subclinical" literally means without clinical symptoms or signs. In fact, the report of symptoms depends to a large extent on the sensitivity (and anxiety?) of the patient, and the finding of signs on the experience and the zeal of the doctor. So, since "subclinical" hypothyroidism is rather a vague term, it should be better called "minimal thyroid failure" and defined by laboratory rather than unprecise clinical criteria. One definition is "increased TSH with normal free serum thyroxine (fT4) and triiodothyronine (fT3) levels"1,2. Others call subclinical hypothyroidism the situation with normal serum fT4 and fT3 values and moderately high serum TSH, say up to 10 mU/l, considering very high TSH values as denoting overt hypothyroidism, even if serum fT4 and fT3 are normal. This last definition, i.e. normal fT4 and fT3 with a TSH between 4.01–10.00 mU/l, is the one preferred by the author.