Dyslipidemia in Subclinical Hypothyroidism: A Case-Control Study Bayar Qasim 1* , Sardar Arif 2 , Ayad Mohammed 2 and Rezvan Abduljabbar 3 1 Department of medicine, College of Medicine, University of Duhok, Duhok, Iraq. 2 Department of surgery, College of Medicine, University of Duhok, Duhok, Iraq. 3 Hematology Oncology Center, Azadi Teaching Hospital, Duhok Directorate of health, Iraq. Journal of Endocrinology and Diabetes Open Access Research article Abstract Subclinical hypothyroidism (SCH) affects 7.5-8.5% of women and 2.8-4.4% of men. Overt hypothyroidism is characterized by dyslipidemia, however controversy persists regarding the lipids level in SCH and its clinical significance. Recent evidence shows that T4 replacement therapy may improve lipid profile. The aim of this study is to assess the prevalence of dyslipidemia in SCH, this first study to assess dyslipidemia among patients with SCH in Duhok, Iraq is a case-control study, comparing 60 patients diagnosed with subclinical hypothyroidism to 60 healthy individuals (matched for age and gender). The study conducted at the endocrine clinic at Azadi Teaching Hospital in Duhok Governorate, Kurdistan Region, Iraq from 1 st June 2016 to 1 st June 2017. Dyslipidemia was much more prevalent in patients with SCH compared to control group (p<0.001). In further analysis of dyslipidemia total cholesterol and triglyceride levels were statistically higher among cases in comparison to controls (p<0.001) for both. LDL level was higher among cases in comparison to controls but did not reach statistical significance (p= 0.087). While there was significant difference regarding HDL level among female gender cases and controls (p= 0.003), there was no significant difference regarding difference in HDL level among male gender cases and controls (p= 0.653).SCH is considered atherogenic condition as it increases dyslipidemia and it increases overall cardiovascular risk. It’s important to assess lipid profile and CVS risk in these patients and to treat with levothyroxine when it’s clinically applicable Keywords: Dyslipidemia, Subclinical hypothyroidism (SCH), Case control study. Received: December 20, 2017; Accepted: January 03, 2018; Published: January 12, 2018 *Corresponding author: Bayar Qasim, University of Duhok School of Medicine, Azadi Teaching Hospital, 8 Nakhoshkhana Road, 1014 AM, Dohuk City, DUHOK, Iraq. ORCID: 0000-0002-0994-7861; Tel: 009647507599548 ;Email: Bayarsabc@gmail.com Symbiosis www.symbiosisonline.org www.symbiosisonlinepublishing.com Symbiosis Group * Corresponding author email: Bayarsabc@gmail.com Introduction Thyroid disorders may occur at any stage of life. They are more commonly encountered in the mid age and adulthood. Thyroid hormones influence nearly all major metabolic pathways. Their most obvious and well-known action is the increase in basal energy expenditure obtained by acting on protein, carbohydrate and lipid metabolism. The lipid metabolism is more influenced by the thyroid hormone [1]. Thyroid hormones are of vital importance in maintaining the initial level of phospholipids in cell membranes and fatty acids composition of the lipids [2]. Tri- iodothyronine (T3) plays a critical role in lipid metabolism by regulating genes involved in lipogenesis and lipolysis [3, 4]. Hypothyroidism results from reduced secretion of both thyroxine (T4) and T3. Biochemically decrease in T4 and T3 concentrations leads to increased serum thyroid stimulating hormone (TSH) level[5,6].Overt hypothyroidism is characterized by hypercholesterolemia and a marked increase in LDL because of a decreased fractional clearance of LDL by a reduced number of LDL receptors in the liver. However controversy persists regarding the lipid levels in subclinical hypothyroidism(SCH) and its clinical significance [1,7]. Asymptomatic patients with raised TSH and normal FT4 concentration are known as subclinical hypothyroid. SCH is mild thyroid disorder if left untreated leads to overt hypothyroidism in many cases. Patients of SCH are mostly asymptomatic or have minimal symptoms. Thus, SCH is solely a laboratory diagnosis [5]. Although clinical diagnosis of thyroid dysfunction is suspected by the presence of a small goiter[8].It is a common condition affecting 6-17% of the general population [9]. The incidence of SCH is more common in women than men, almost twice [10]. Worldwide prevalence of SCH is found to be 7.5- 8.5% in women and 2.8-4.4% in men [11]. The diagnosis is based upon biochemical testing which is done by chemiluminiscence technique. The normal TSH range is 0.4 – 4.5 mIU/L TSH[5]. Subclinical hypothyroidism is a risk factor for increased incidence of coronary events, increased rates of congestive heart failure and lipid abnormalities. Dyslipidemia is one of many modifiable and non-modifiable cardiovascular risk factors like diastolic hypertension, impaired endothelial function, increased arterial stiffness, and coagulation parameters and elevated C-reactive protein levels are associated with subclinical hypothyroidism[11]. The Pathophysiology lies behind the lipid alterations of overt and SCH includes elevations in serum total cholesterol due to changes in the synthesis, metabolism, and mobilization of lipids in liver and adipose tissue. High TSH level induces the hepatic expression of hydroxy methyl glutaryl coenzyme A reductase, which results in increased cholesterol synthesis [12]. In hypothyroid patients the most frequent lipid abnormality is