Introduction: Both thyroid diseases and diabetes mellitus (DM) are common in medical practice in Saudi Arabia. This research was done to study the possible relation between these two diseases.

Materials and Methods: A prospective case control study was carried out to assess thyroid abnormalities by Ultrasound (US) in diabetic patients (type 1 and type 2 ).The study population consisted of 69 diabetic patients (20 Type 1DM and 49 Type 2DM) and 111 non diabetic patients. Thyroid US was done for all participants and thyroid function test mainly thyroid stimulating hormone (TSH) was done for all cases that showed positive US changes for thyroid abnormalities.

Results: Abnormal thyroid US was detected in 66.7% of diabetic and 34.2% of non diabetic participants. Multinodular goitre (MNG) was the most common disorder in both types of  DM (78.6% in DMT1 and 56.3% in DMT2), while thyroid nodules were the least common disorder. No significant difference between diabetic and non diabetic patients in TSH results.

Conclusion and Recommendations: The present study showed high prevalence of thyroid disorder in diabetic patients. We recommend routine US for all diabetic patients especially those with long term diabetes, uncontrolled diabetes or complaining of symptoms of thyroid dysfunction.