Rajiv Gandhi University of Health Sciences, Karnataka, Bangalore s4

RAJIV GANDHI UNIVERSITY OF HEALTH SCIENCES, KARNATAKA, BANGALORE.

6 Brief resume of intended work

6.1 Introduction and need for the study

Hypothyroidism is a common endocrine disorder that occurs due to the deficiency of thyroid hormone or its effect on peripheral tissue. The prevalence of hypothyroidism in adults is around 10.95% in India1.

Classically the role of vitamin D is defined in calcium/phosphorus homeostatis and bone development. As most tissues and cells in the body have vitamin D receptors and several cells possess the enzymatic machinery to convert 25(OH)D3 to its active form2,this has provided new insight into the functions of this vitamin.

This study is being done to see if there is any correlation between serum vitamin D [25(OH)D] levels and primary hypothyroidism. Besides, TPOAb positivity and its correlation to vitamin D will also be estimated in these cases of primary hypothyroidism.

6.2 Review of literature

Hypothyroidism is classified as-

1. Primary Hypothyroidism-Due to insufficient production of thyroid hormone by thyroid gland.

2. Secondary Hypothyroidism-Due to insufficient production of TSH from pituitary gland.

3. Tertiary Hypothyroidism-Due to inadequate secretion of TRH from hypothalamus.

The most common cause of primary hypothyroidism in adults is autoimmune thyroid disease like Hashimoto’s thyroiditis.

Vitamin D is a prohormone synthesized endogenously by conversion of 7-dehydrocholesterol to vitamin D3 by exposure of skin to UVB rays of sun. It is metabolized first to its main circulating form 25(OH)D by 25 hydroxylase in liver then to its biologically active form 1,25(OH)2D by 1-alpha hydroxylase in kidney.

Serum 25(OH)D level is a better indicator of vitamin D status3 than 1,25(OH)2D because-

1.  25(OH)D is the main circulating form of vitamin D.

2.  Serum 25(OH)D has longer half life as compared to 1,25(OH)2D.

3.  The technique to measure serum 25(OH)D is simpler than the more complicated methods for measuring serum 1,25(OH)2D.

According to clinical practice guidelines4 given by Endocrine Society of USA vitamin D deficiency is defined as serum 25(OH)D below 20 ng/ml, vitamin D insufficiency as serum 25(OH)D of 21-29 ng/ml.

It has been seen in various studies that there is an inverse relationship exists between serum vitamin D levels and autoimmune thyroiditis. Chaiourkit L5 et al has seen in their population based health study that higher 25(OH)D levels were independently associated with lower TSH in younger individuals.

Results of the study done by Goswami R et al6 indicated the presence of a significant inverse association between 25(OH)D levels and TPOAb positive autoimmune thyroid disease.

6.3. Objectives of study:

1.  To estimate the serum 25(OH)D levels in patients with newly diagnosed primary hypothyroidism and to compare with normal healthy controls.

2.  To estimate serum TPOAb levels in these patients of primary hypothyroidism and to compare with normal healthy controls.

3.  To find association between vitamin D deficiency / insufficiency and primary hypothyroidism

7. Materials and methods:

7.1 Source of data:

Cases: Patients diagnosed with primary hypothyroidism having serum TSH level 4.5µ IU/ml and serum T4 level normal or decreased7 reporting to M .S. Ramaiah Hospitals. Investigations done for thyroid function test will be serum T3, serum T4 and serum TSH.

Controls: Clinically healthy individuals with normal TSH level3 who are willing to be part of this study. Data of controls will be registered in hospital records.

Study design: Case control cross sectional study

7.2 Method of collection of data:

GROUP 1: CASES – 56 Patients (males and pre-menopausal females) in the age group 20-50 years diagnosed as having primary hypothyroidism.

GROUP 2: CONTROL – 28 Clinically healthy individuals (males and pre-menopausal females) in the age group 20-50 years.

Sample collection will be collected over a period of one year starting from January 2014. Informed written consent from all the cases and controls will be taken for this study.

Sample size estimation:

According to various studies conducted on Indian population, prevalence of vitamin D deficiency ranges from 50-90%(Editorial,JAPI.NOVEMBER2011.VOL.59) while vitamin D deficiency amongst patients with primary hypothyroidism due to Hashimoto’s thyroiditis has been reported to be 98.2% in a study carried out in Turkey by Bozkurt et al8. Based on the above findings with the power of 75%, alpha error of 5% and allocation ratio of 1:2, it is estimated that 56 cases and 28 controls need to be included for the study, matched for age and gender(frequency matching).

Inclusion criteria:

1.  Cases: Age group 20-50 years, male and pre-menopausal female patients with serum TSH level 4.5µ IU/ml and serum T4 level increased or normal.

2.  Controls: Age group 20-50 years, male and pre-menopausal female, clinically healthy individuals.

Exclusion criteria

1. Pregnant females and lactating mothers.
2. Postmenopausal women
3. History of diabetes mellitus
4. History of thyroidectomy or radio-iodine ablation
5. Patients with hepatic disease, renal disease, acute illnesses, infections
6. Patients admitted for surgery
7. Patients on bisphosphonates, calcium supplements, steroids, anti-epileptics, anti-thyroid drugs, oral contraceptives, diuretics, amiodarone.
8. History of intestinal malabsorption disorder, vitamin D deficiency/ insufficiency,

Vitamin K insufficiency, fractures or malignancy.

1. History of any other autoimmune disorders.

Blood sample will be collected from each study subject. Following lab investigations will be done on the samples:

·  Serum 25(OH)D levels - Enzyme Linked Immunosorbent Assay(ELISA) kit method

·  Serum TPOAb levels - Enzyme Linked Immunosorbent Assay(ELISA) kit method

·  Serum TSH levels - Electro Chemiluminescence Immunoassay(ECLIA) method

·  Serum T4 levels - Electro Chemiluminescence Immunoassay(ECLIA) method

·  Serum T3 levels - Electro Chemiluminescence Immunoassay(ECLIA) method

Statistical analysis:

Quantitative parameters such as serum 25(OH)D levels, serum TPOAb levels, age will be expressed as mean ± standard deviation for both group of subjects. Proportion will be estimated for qualitative variables. For various diagnostic parameters sensitivity, specificity, NPV, PPV and accuracy will be estimated. Differences in the sensitivity and specificity will be tested for statistical significance through the chi-square test of significance.

7.3 Does the study require any investigations to be conducted or interventions to be conducted on patients or other humans or animals? If so please describe briefly.

Yes. Described in 7.2.There will be no financial liability on the patients/controls. All expenses will be borne by the investigator.

7.4  Has ethical clearance been obtained from your institution in case of 7.3?

Yes.

8. List of References

1.  Unnikrishnan AG, Kalra S, Sahay RK, Bantwal G, Jhon M, Tewari N. Prevalence of hypothyroidism in adults: An epidemiological study in eight cities of India. Indian J Endocrinol Metab. 2013 Jul; 17 (4): 647-52.

2.  Norman AW. Minireview: vitamin D receptor: new assignments for an already busy receptor. Endocrinology. 2006 Dec; 147 (12): 5542-8.

3.  David BE, Roberts KR. Disorders of Bone In Carl AB, Edward RA, David EB Tietz Fundamentals of Clinical Chemistry Sixth Edition. New Delhi; Reed Elsevier India Private Limited; 2013: 725

4.  Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA,Heaney RP et al; Endocrine Society. Evaluation, treatment and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011 Jul; 96 (7): 1911-30.

5.  Chailurkit LO, Aekplakorn W, Ongphiphadhanakul B. High vitamin D status in younger individuals is associated with low circulating Thyrotropin. Thyroid. 2013 Jan; 23 (1): 25-30.

6.  Goswami R, Marwaha RK, Gupta N, Tandon N, Sreenivas V, Tomar N et al. Prevalence of vitamin D deficiency and its relationship with thyroid autoimmunity in Asian Indians: a community based survey. Br J Nutr. 2009Aug; 102(3): 382-6.

7.  Garber JR, Cobin RH, Gharib H, Hennessey JV, Klein I, Mechanik JI et al. American Association of Clinical Endricologists and American Thyroid Association Taskforce on Hypothyroidism in Adults.Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012 Nov-Dec; 18 (6): 988-1028.

8.  Bozkurt NC, Karbek B, Ucan B, Sahin M, Cakal E , Ozbek M et al. The association between severity of vitamin D deficiency and Hashimoto’s thyroiditis. Endocr Pract. 2013 May-Jun; 19 (3): 479-84.