Down syndrome (DS) is caused by an extra chromosome 21 and is the most common autosomal chromosome aberration. Down syndrome results in mental retardation and several congenital malformations. The aim: The purpose of this study is to shed light on the importance of follow-up screening analysis of some hormones and some biochemical parameters in patients with Down syndrome. Methods: Laboratory variables in 31 adult patients with Down's syndrome were compared with those of 30 matched controls. Fasting blood samples were collected for estimation of free thyroxin (FT4), thyroid stimulating hormones (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), free testosterone (T), as well as serum levels of creatinine, uric acid and albumin. Results: The thyroid function tests documented a higher mean TSH and lower FT4 mean levels in Down's syndrome than in controls. FSH and LH mean levels were significantly higher in DS group than in controls (p<0.05). The mean level of estradiol (E2) in females with DS (11.61±2.28 pg/ml) was significantly lower than controls (31.18±2.71 pg/ml) (p<0.05), while the level of free testosterone (fT) was significantly higher compared with control subjects (2.71±0.66 pg/ml versus 1.2±0.37 pg/ml respectively, p<0.05. As well as, in males DS patients, the level of E2 was normal (11.33±1.04 pg/ml) while the level of free testosterone was significantly lower compared with controls (1.98±0.21 pg/ml) and (2.63± 0.44 pg/ml) respectively. Also, levels of serum creatinine and uric acid in DS patients were higher compared with controls, while the level of albumin was low (p<0.05). Conclusion: Through the results of measuring some hormones and biochemical changes in this study of Down syndrome patients compared to healthy subjects, it turns out DS patients are more vulnerable to diseases than others, such as renal and hepatic diseases, infertility and should be followed to keep under control.