Thymic endocrine activity in children with idiopathic growth-hormone deficiency

Experimental and clinical evidences suggest that thymic endocrine function is modulated by the neuroendocrine network and in particular by growth hormone. The plasma of thymulin has been found reduced in congenital hypopituitarism and increased in acromegalic conditions when compared with the values observed in age-matched controls. In the present paper we have investigated in congenital GH-deficient children the effect of one year therapy with GH on the plasma level of thymulin, IGF-1 and plasma zinc; this last parameter has been checked because zinc is required for thymulin activity and modulates IGF-1 production. The basal thymulin and IGF-1 values are lower in GH deficient children than age-matched controls whereas zinc levels show a slight reduction. GH therapy induces a significant increment both of thymulin and IGF-1 levels and a slight increase of plasma zinc. A positive correlation has been found between zinc values and thymulin activity but not between GH and thymulin. Whether the recovery of thymulin production in GH deficient children by GH therapy is mediated by IGF-1 or by bioavailability of zinc ions remains to be established.