triiodothyronine--reverse and Thalassemia

Thyroid function was evaluated in 20 patients aged 8-30 years who were suffering from homozygous beta-thalassaemia. All patients have been receiving frequent blood transfusions and treated for the resulting transfusional iron overload with intramuscular injections of Desferrioxamine. Total thyroxine (T4), T3-uptake, total triiodothyronine (T3), and reverse triiodothyronine (rT3) were measured. In addition a standard TRH stimulation test was performed and blood samples were checked for the presence of thyroid antibodies. It was found that total T4 was significantly lower in the patients than in the controls. Total T3 and rT3 levels were similar in both patients and controls and all patients were negative for thyroid antibodies. T3 uptake in the patients was also statistically different from the controls resulting in significantly lower free thyroxine index (FT1). Basal TSH values were not different from the controls but the TSH increase following TRH stimulation was significantly higher in the patients suggesting, together with the low total T4 and FTI, a state of compensated hypothyroidism.

Topics: Adolescent; Adult; Child; Female; Homozygote; Humans; Male; Thalassemia; Thyroid Function Tests; Thyroid Gland; Thyrotropin; Thyrotropin-Releasing Hormone; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse

Thyroid function has been evaluated in 6 prepubertal male and 9 female thalassemic patients. Four of the latter were sexually immature (Group I), with very low estradiol levels and the remainder had more advanced sexual development (Group II). Subjects were challenged with TRH and the response compared to adult controls and a group of 15 males aged 13-18 years with constitutional delayed adolescence. All patient groups and controls had normal levels of T4, T3 and T3 resin uptake. When compared to adult controls or males with constitutional delayed adolescence, the male thalassemic patients had increased basal TSH levels with an exaggerated response to TRH. Long term testosterone enanthate led to a decrease in integrated TSH secretion, showing that androgens may decrease the TSH response to TRH. The more sexually mature females of Group II also had increased basal and stimulated TSH levels; however, the sexually immature females of Group I had basal TSH and TSH responses to TRH equivalent to female controls. In Group I patients there were, moreover, no changes in TSH response during administration of estradiol valearate for 3 months and conjugated estrogens for 8 months. The high basal and stimulated TSH levels in the males and Group II females are most likely due to subclinical primary hypothyroidism. This has been previously described in thalassemia. On the other hand, failure of estrogens to increase the TSH response to TRH in Group I females is evidence of pituitary involvement, which is also well documented in this clinical condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adolescent; Adult; Estradiol; Female; Humans; Male; Puberty, Delayed; Sex Factors; Thalassemia; Thyroid Function Tests; Thyrotropin; Thyrotropin-Releasing Hormone; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse

Topics: Adolescent; Blood Transfusion; Child; Deferoxamine; Female; Humans; Male; Pituitary Gland, Anterior; Thalassemia; Thyroid Gland; Thyroid Hormones; Thyrotropin; Thyrotropin-Releasing Hormone; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse

Serum concentrations of T4, T3, rT3, and TSH were measured by radioimmunoassay in 45 patients suffering from beta-thalassaemia. A TRH stimulation test was performed and the binding capacity of TBG and TBPA for T3 and T4 measured by reverse flow zone electrophoresis in a group of these patients. Mean T4 serum concentration was lower in thalassaemic patients than controls; T3, rT3, TSH levels, and the pituitary response to TRH were normal. TBPA binding capacity for thyroxine was greatly decreased, probably due to iron overload impairing the liver function. The decreased circulating total thyroxine might be explained by the reduced TBPA capacity, serum free thyroid hormone concentration total thyroxine might be explained by the reduced TBPA capacity, serum free thyroid hormone concentration values being normal. It is concluded that thalassaemic children are euthyroid, despite often having low-normal or subnormal thyroxine levels.

Topics: Adolescent; Adult; Child; Child, Preschool; Humans; Infant; Thalassemia; Thyroid Gland; Thyrotropin; Thyrotropin-Releasing Hormone; Thyroxine; Thyroxine-Binding Proteins; Triiodothyronine; Triiodothyronine, Reverse