Known since 1967 and usually familial, the syndrome of tissue resistance to 
thyroid hormones may take one of two different forms, depending on the receptors 
involved. When resistance affects both peripheral and pituitary receptors, 
plasma thyroid hormone levels are high despite the lack of thyrotoxicosis, 
thyroxine and triiodothyronine are ineffective, even in high dosage, and plasma 
TSH increases to explode under TRH. When resistance only affects pituitary 
receptors, there is moderate thyrotoxicosis with paradoxical and inappropriate 
TSH increase. Contrary to expectations, nuclear receptors to triiodothyronine 
are perturbed in only a few cases. Reduction of thyrotropic hyperfunction, which 
is the primary purpose of treatment, can be achieved with D-forms of thyroid 
hormones or with somatostatin and its derivatives.