Incidence of Vitamin B12 Deficiency in Patients with Hypothyroidism
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Jebmh.com Original Research Article Incidence of Vitamin B12 Deficiency in Patients with Hypothyroidism Priyadarshini Raju1, Shreyas Kumar V.2 1, 2 Department of General Medicine, Rajarajeswari Medical College, Bangalore, Karnataka, India. ABSTRACT BACKGROUND Hypothyroidism is a common endocrine disorder which affects 11 % of the adult Corresponding Author: population in western countries. Hypothyroidism can cause a wide variety of Dr. Priyadarshini Raju, # 2215, 4th A Cross, 4th Main, anaemic disorders. Patients with both hypothyroidism and Vitamin B12 deficiency Hampinagar, Bangalore – 560104, also have similar symptoms. Thus, this study was conducted to evaluate the Karnataka, India. relationship between the two and also hypothyroidism due to autoimmune cause. E-mail: [email protected] METHODS DOI: 10.18410/jebmh/2021/81 This was a descriptive study of 50 newly detected hypothyroid patients from Rajarajeswari Medical College evaluated for vitamin B12 deficiency. The study was How to Cite This Article: conducted between January 10th 2019 to July 21st 2019. Lab parameters analysed Raju P, Kumar VS. Incidence of vitamin B12 deficiency in patients with included haemoglobin, thyroid function test (TFT), vitamin B12 levels and anti- hypothyroidism. J Evid Based Med thyroid peroxidase (anti-TPO) antibody levels. Healthc 2021;8(08):415-419. DOI: 10.18410/jebmh/2021/81 RESULTS Of the 50 hypothyroid patients evaluated, 23 were males and 27 were females Submission 17-08-2020, between the age of 18 to 70 years. Anti TPO antibodies were present in 24 Peer Review 25-08-2020, patients (48 %) out of 50, out of which 17 (70 %) patients had vitamin B12 Acceptance 04-01-2021, deficiency. Out of 50 hypothyroid patients, 26 patients (52 %) had vitamin B12 Published 22-02-2021. deficiency. Thus hypothyroidism and autoimmune thyroid disease was associated Copyright © 2021 Priyadarshini Raju et with Vitamin B12 deficiency which was statistically significant. al. This is an open access article distributed under Creative Commons CONCLUSIONS Attribution License [Attribution 4.0 Patients with hypothyroidism were studied for the incidence of deficiency of International (CC BY 4.0)] vitamin B12. It was found that 26 of 50 (52 %) patients had low B 12 levels. Incidence in females (54 %) was more than in males (46 %). Our study showed association between hypothyroidism and vitamin B12 deficiency and also autoimmune thyroid disease. KEYWORDS Hypothyroidism, Autoimmune Thyroid Disease, Vitamin B12 Deficiency J Evid Based Med Healthc, pISSN - 2349-2562, eISSN - 2349-2570 / Vol. 8 / Issue 08 / Feb. 22, 2021 Page 415 Jebmh.com Original Research Article BACKGROUND Malabsorption usually occurs due to inability to break free B12 which is present bound to protein. Bariatric surgery Vitamin B12 (B12) also known as cobalamin1 has a patients are at increased risk of developing vitamin B12 chemically complex structure. It is the largest of all vitamins. deficiency and also require lifelong supplementation through At the centre of a corrin ring, it contains an atom of cobalt diet. and is the only active substance in the body. In the H. pylori infection, chronic inflammation of gastric mitochondria it exists in 2-deoxyadenosyl (ado) form which mucosa and long-term antacid therapy leads to is the cofactor for the enzyme L–methyl malonyl coenzyme- malabsorption as they adversely affect gastric acid and A (CoA) mutase. Methyl cobalamin which is the cofactor of pepsin secretion. methionine synthase is the other major cobalamin occurring The reduction in the availability of functional gastric naturally. Purine and pyrimidines synthesis requires mucosa and reduced secretion of intrinsic factor lead to methionine synthase. The reaction in which methyl group of vitamin B12 deficiency. Chronic inflammation of gastric methyl tetrahydrofolate is transferred to homocysteine to mucosa leading to atrophic changes leading to reduce IF, form tetrahydrofolate and methionine. Megaloblastic diminished HCl production resulting in pernicious anaemia. anaemia develops due to interruption of this reaction. It is an autoimmune disorder which contains anti intrinsic 5 Transcobalamin II is the active transport protein for factor antibodies and anti-gastric parietal cell antibodies. It vitamin B12. The endogenous forms consist of cobalamin is the end stage of an auto immune gastritis which results in and holotranscobalamin. The reduced state is treated with loss of intrinsic factor. Vitamin B 12 deficiency can also occur cyanocobalamin. due to reduced ileal uptake due to diseases such as Crohn’s, Vitamin B12 is synthesised solely by anaerobic chronic inflammatory conditions. Drugs such as proton pump microorganisms. The food of animal origin is the only source inhibitors, metformin, nitrous oxide anaesthesia, epileptic available for humans which includes fish, meat, poultry, medications and colchicine lead to vitamin B 12 deficiency. dairy and eggs. There are no naturally occurring active forms Symptoms and signs of vitamin B 12 takes several years of vitamin B12 from plant sources. It is also available in the to manifest. B12 deficiency leads to haematological, supplements and fortified foods in crystalline form.2 The neurological, cardiovascular and psychiatric manifestations. bioavailability of vitamin B12 depends on individual’s Clinical features include fatigue, pallor, dementia, peripheral gastrointestinal absorption capacity. The supplements neuropathy, ataxia and loss of proprioception. Clinical signs contain cyano form, which is also found in trace amounts in of B 12 deficiency may be subtle and missed if not detected food. Deficiency results from reduced consumption, reduced by a laboratory evaluation of vitamin B 12. B 12 induced absorption, autoimmune states or genetic disorders. nerve damage may cause peripheral neuropathy. Cobalamin absorption consists of two mechanisms, Evaluation in suspected cases is done with complete active and passive. Passive mechanism occurs via the blood count with a peripheral smear, serum vitamin B 12 buccal, duodenal and ileal mucosa but is inefficient. The levels and folate levels. Other tests include methylmalonic active mechanism is the normal physiologic mechanism, acid (MMA) and homocysteine levels. Treatment involves occurs through ileum and is mediated by the intrinsic factor repletion with B 12. (IF). Hydrochloric acid which is produced by the gastric Hypothyroidism is defined as abnormally low activity of mucosa is required to separate the vitamin B12 which is the thyroid gland, resulting in retardation of growth and bound to the protein. This released cobalamin binds to R mental development in children and adults. It is divided into protein and reaches duodenum where R protein gets primary and secondary according to level of endocrine separated. Intrinsic factor binds to the free cobalamin and is dysfunction. It also has congenital and acquired types absorbed by distal ileum. Vitamin B12 is secreted in bile depending on the time of onset of the disease. Depending which via the ileal receptors gets reabsorbed into on the severity, it is divided into mild, subclinical and overt enterohepatic circulation. This process requires intrinsic types. The main thyroid hormones are Thyroxine (T4) and factor. Intrinsic factor deficiency leads to pernicious Triiodothyronine (T3). T4 is produced only from thyroid anaemia. About 0.1 % gets excreted per day. Excess vitamin gland, whereas T3 is produced from thyroid and peripheral B12 gets excreted in urine. deiodination of T4. Hormones of thyroid gland help in 3 - 4 % of the general population have vitamin B12 production of erythroid colonies. This occurs with the help deficiency. The reduced state is very rare in kids and of erythropoietin. Underactive thyroid leads to anaemia. 6 adolescents. Vitamin B12 helps in central nervous system Hypothyroidism can cause a variety of anaemic disorders. myelination, synthesis of nucleic acids and erythropoiesis. A The underactive thyroid leading to reduced synthesis and sufficient contribution of B12 is necessary to support the production of thyroid hormones is known as primary functions.3 Malabsorption and reduced consumption through hypothyroidism. 50 % of the cases are of autoimmune diet are not the uncommon reasons for reduced state of B12, aetiology. which is usually seen in the elderly.4 Strict vegetarians are Autoimmune thyroid diseases (AITD) encompass a group prone to B12 deficiency and can meet their requirements of disorders characterised by antibodies against thyroid from supplements and fortified foods. Vegetarian pregnant gland such as Hashimoto’s thyroiditis and Graves’ disease. and lactating women are at high risk of deficiency and AITD occurs more commonly in women between the ages of require adequate intake of vitamin B12 supplements. 40 to 60. There is infiltration of lymphocytes and also distinct Undernutrition is common among the elderly due to physical antibodies circulate in hypothyroidism due to autoimmunity. capacity, illnesses and inflammation of gastric mucosa. Presence of thyroid autoantibodies in serum is necessary for J Evid Based Med Healthc, pISSN - 2349-2562, eISSN - 2349-2570 / Vol. 8 / Issue 08 / Feb. 22, 2021 Page 416 Jebmh.com Original Research Article the diagnosis of AITD. The main autoantigens of thyroid are METHODS thyroperoxidase (TPO), thyroglobulin and thyroid stimulating hormone receptor (TSH-R). 95 % of cases have Inclusion Criteria increased anti TPO antibodies and 60 % have anti Patients between the ages of 18 to 70