Effect of long-term GH administration on pituitary-thyroid function in idiopathic hypopituitarism

Twenty-four euthyroid children with idiopathic pituitary dwarfism were studied. The euthyroid state for seven of these patients was determined by negative physical examinations, normal plasma T4 assays and normal 131I uptakes. For the other children, thyroid function was evaluated with T3 and T4 assays and on the basis of the TRH test. Each of the children was treated with HGH in one of three different ways. The first group (five cases) was given a HGH dose, ranging from 12.4 to 17.2 IU/m2//week. The second and third groups (nine and ten cases, respectively) were treated with 10 and 20 IU/m2/week, respectively. Treatment was carried out for periods ranging from 6 months to 6 years. After no less than 6 months of treatment, and at intervals of 6 months (or some multiple of 6 months) plasma T3 and T4 assays, as well as a TRH test were performed in each patient. In some patients one of the indices was once beyond the upper or lower limit of the normal range (none of the children presented simultaneous abnormal levels of more than one index during the controls). This value, however, returned to within normal limits at the following control. There was no correlation between T3, T4 and TSH with the duration of HGH therapy. There was no significant difference between the groups of children treated with the different HGH doses. These data seem to demonstrate that the risk of inducing an alteration in thyroid function in hypopituitary patients during HGH treatment is very slight, and that the irregularly abnormal thyroid indices observed in some of the children during one of the controls might be an expression of their metabolic status at that moment.