Change in serum concentration of insulin-like growth factor II (IGF-II) in patients with thyroid disease

We investigated the serum concentration of IGF-II in patients with thyroid diseases (25 with untreated Graves' patients, 30 with hypothyroidism, 23 with thyroid adenoma) and in 72 healthy adults as normal controls, by a sensitive radioimmunoassay of serum IGF-II. Thyroid hormones are known to increase IGF-I production in the liver through the enhancement of GH secretion. In case of IGF-II, however, knowledge has been rather limited. The mean +/- SD concentration in healthy subjects was 556 +/- 94 micrograms/L with neither sex nor age dependence. In untreated Graves' patients, serum IGF-II levels (675 +/- 129 micrograms/L) were significantly (P < 0.01) higher than in normal controls, and significantly lower in patients with hypothyroidism (460 +/- 106 micrograms/L; P < 0.01). Thyroid hormones revealed positive correlation with the IGF-II concentration.