Abstract
In a 41 year-old patient with Klinefelter's syndrome, a failure of TRH-induced TSH secretion was noticed. Low 131I-thyroid uptake, together with the elevation following exogenous TSH administration, indicates that the defective locus exists in the hypothalamus or pituitary resulting in an impaired secretion of TSH. Such a defect may underlie thyroid dysfunction often associated with Klinefelter's syndrome.
