This study was carried out in Kasr El Eini University hospital under the supervision of Prof. Dr. Sarah EL Kateb (Chemical Pathology department), Prof. Dr. Nadida Gohar (Chemical Pathology department) and Prof. Dr. Khadiga El Ashmawy (Internal Medicine). The study was done with the aim of finding a correlation between serum levels of IGF-I and IGFBP-3 in relation to the functional status of the thyroid gland. The study was conducted on a total number of 80 cases classified into 3 group: the hypothyroid group (30 patients) and the hyperthyroid group (30 patients), both groups were compared to20 age and sex-matched apparently healthy subjects as the control group. The hypothyroid group was further subdivided into 3 subgroups: 10 newly diagnosed cases not receiving medication, 12 subclinical cases and 8 cases under medical treatment. The hyperthyroid groups was further subdivided into 2 subgroups: 22 newly diagnosed cases not receiving medical treatment and 8 cases under medical control. All of the cases and controls were subjected to full thyroid profile (FT3 (RIA), FT4 (RIA) and TSH (ELISA chemiluminescence) in addition to serum estimation of IGF-I and IGFBP-3 (IRMA). Mean serum levels of IGF-I and IGFBP-3 Z values were significantly higher in the hyperthyroid group when compared with hypothyroid group. The mean serum IGF-I Z value was significantly higher in overt cases of hyperthyroidism when compared with hyperthyroid cases under treatment. Mean while the mean serum IGF-I Z value was significantly lower in clinical case of hypothyroidism on comparing it with the control group. Also a highly significant positive correlation was found between serum IGF-I and IGFBP-3 z values in all of 3 studied groups and a highly significant negative correlation was found between serum IGF-I Z value and TSH level in all cases and controls. Finally, further studies are recommended to study the relation between IGF-I and its binding protein-3 serum concentration and thyroid dysfunction on a larger numbers of patients and different degrees of illness, and studying the possibility of using recombinant IGF-I as an adjunctive to L-thyroxin replacement therapy in hypothyroidism, as well as in monitoring the effect of treatment and follow up of cases in hyperthyroidism.