The endocrine organs are more susceptible to iron deposition and the resulting dysfunction can lead to significant morbidity. These com plications are seen at higher frequencies in poorly chelated individuals and with improved chelation compliance with the oral agents it is anticipated that the incidence of these complications will decline. Regular monitoring for these complications is recommended, especially in those individuals with a history of more significant iron over load and poor chelation compliance.
Growth. Growth retardation, including skeletal and dental deformities, was common even in young children until the use of hyper transfusion regimens was instituted. With the correction of the severe anemia, growth was initially restored to relatively normal during the first decade of life, unless heavy iron deposition in the pituitary resulted in growth hormone deficiency early. Without appropriate iron chelation therapy, the adolescent growth spurt is often delayed or absent; most patients, even those well maintained by transfusion, may not attain normal stature, partly because of iron-induced dam age to the anterior pituitary. Menarche is frequently delayed. Breast development may be poor, and many female patients have primary or secondary amenorrhea. Boys are frequently immature, with sparse facial and body hair. Although spermatogenesis may be normal at least initially, libido is often decreased as a result of decreased testosterone secretion. An older multicenter study of 250 adolescent patients in northern Italy showed that despite hypertransfusion and 7 to 10 years of deferoxamine iron chelation therapy, two-thirds of male patients and one-third of female patients older than 14 years of age were two standard deviations or more below the mean for height. Many adolescents between 12 and 18 years of age lacked any secondary sexual changes of puberty. However, the mean serum ferritin level in the entire group was 3500 ng/mL, indicating persistence of a high level of excess iron burden in most of this group.
Regular chelation therapy started early in the first decade of life frequently allows a normal onset of puberty and development of secondary sexual changes. If necessary, administration of recombinant human growth hormone in conventional doses increases height velocity in patients with growth hormone deficiency. Normal or higher doses of recombinant human growth hormone increase growth velocity in patients with normal growth hormone reserve but low levels of insulin-like growth factor I. For patients with a functional hypothalamic-pituitary axis, treatment with gonadotropin-releasing hormone may induce pubertal changes. In others, administration of sex steroids is necessary to induce secondary sexual characteristics.
Diabetes. Abnormal carbohydrate metabolism is common in older patients with thalassemia major. Prepubertal children usually have normal glucose metabolism, but pubertal patients exhibit impaired responses to glucose load. Higher than normal insulin levels despite normal glucose levels are also encountered during puberty. The defect in these patients appears to be related to insulin resistance, with insulin deficiency developing later in the progression to diabetes. Rates of diabetes are reported close to 6% to 8%. Diabetes occurs more frequently in patients with hepatitis C and hepatic dysfunction. Oral hypoglycemic agents have been used to regulate hyperglycemia and may reduce the rate of further deterioration of glucose metabolism. It is important to keep in mind that the conventional HbA1C monitoring is not reliable in individuals who are regularly transfused since it measures levels in red cells which have been stored in high concentrations of glucose for variable periods of time. Hence an oral glucose tolerance test is recommended for monitoring for this com plication in individuals at risk.
Thyroid and parathyroid disease. Laboratory findings of hypothyroidism and hypoparathyroidism are present in approximately 14% of patients with thalassemia major. Though clinical findings associated with these deficiencies are uncommon, replacement therapy is recommended.
