The Philippine Thyroid Disorder Prevalence Study (PhilTiDeS)



The Philippine Thyroid Disorder Prevalence Survey (PhilTiDeS)

A project of the Philippine Society of Endocrinology and Metabolism in cooperation with the Food and Nutrition Research Institute-Department of Science and Technology and the Philippine Council on Health and Research Development

By the PhilTiDeS Writing Group:

Carlos-Raboca, Josephine, M.D.,F.P.C.P., F.P.S.E.M.

Jasul, Gabriel A. Jr.,M.D. F.P.C.P., F.P.S.E.M.

Kho, Sjoberg A., M.D. F.P.C.P., F.P.S.E.M.

Jimeno, Cecilia A., M.D. F.P.C.P., F.P.S.E.M.

Andag-Silva Aimee, M.D. F.P.C.P., F.P.S.E.M.

Nicodemus, Nemencio A. Jr., M.D. F.P.C.P., F.P.S.E.M.

Cunanan, Elaine A.,M.D. F.P.C.P., F.P.S.E.M.

Significance of the Study

Disorders of thyroid function, whether hyperthyroidism or hypothyroidism are medical conditions that can have a significant impact on public health and can even shorten the lifespan of individuals of any age. Thyroid disorders, goitrous and non goitrous forms, occur with great frequency in the adult population ranging from 0.5 to 5% in overt disease and 3 to 10% in the subclinical forms depending on the population, age and sex examined(1). While lack of dietary iodine is an important underlying cause of thyroid disorders, excess iodine , genetic background, other geographical and dietary factors can trigger thyroid disorders.(2) Children, pregnant women and lactating mothers are most at risk to iodine deficiency as this may result in permanent damage to the developing brain. In the general adult population which is the backbone of the labor force of a country, deficient and excessive iodine can cause subtle thyroid abnormalities with considerable consequences. Small aberrations in thyroid function have been associated with overweight and blood pressure problems.(3,4,5) The elderly are most susceptible to the cardiovascular consequences of this disease even in the subclinical or the mild form which can only be determined by biochemical thyroid function tests. This underlies the importance of timely detection of thyroid disorders

The frequency of thyroid disorders varies in countries. A national prevalence study among Filipino adult population using thyroid function tests, which has never been done before, will give us information vital to public health. Data on thyroid disorders which will include the overt clinical forms and subclinical forms of the disease, estimate of national burden of illness, distribution by age and region can help us formulate strategies and guidelines to improving medical care in thyroid disorders among Filipinos.

Literature Review: The national prevalence of goiter was first reported in 1987. Clinical examination for the presence of goiter was undertaken during the 1987 and 1993 National Nutrition Surveys allowing comparisons. Previous studies only documented the prevalence of goiter based on clinical examination. There appeared to be an increase in the prevalence of goiter during this six-year period, with the initial rate in 1987 of 3.7% to 6.7% in 1993 (Phil. F&F, 2001). In the latter data, the highest prevalence rate was seen in pregnant women aged 13 to 20 years at 27.4%.

This study will be the first national survey in the Philippines on the prevalence of thyroid disorder based on thyroid function tests.

Objectives:

General Objective:

To determine the prevalence of abnormal thyroid function among the general adult population.

Specific Objectives:

Among non-pregnant/lactating adults:

1. To determine the prevalence of:

a. Overt Hyperthyroidism and sub-clinical hyperthyroidism

b. Overt Hypothyroidism and sub-clinical hypothyroidism

c. Thyroid nodules

d. Iodine deficiency goiters

2. To evaluate the sufficiency of iodine nutrition based on the urinary iodine excretion

3. To determine the relationship between abnormal thyroid function and:

a. Lipid levels

b. Clinical symptoms and signs as assessed by the modified Wayne's index

Methodologies:

Sampling Design

The PhilTiDeS will involve the subjects of the 7th National Nutrition Survey using National Statistics Office’s (NSO) Labor Force Survey (LFS) Sample. The Biochemical and Clinical components in particular will cover 50% of sampled households therein, permitting national and regional estimates for the selected variables.

The 2008 Labor Force Survey, and therefore also the 7th NNS, will employ a stratified multi-stage sampling design, covering all 17 regions and 80 provinces. The first stage of sampling is the selection of Primary Sampling Units (PSUs), a PSU being a barangay or contiguous barangays with at least 500 households; followed by the selection of Enumeration Areas (EAs), an EA being a contiguous area in a barangay, or a barangay with at least 150 – 200 households, and the selection of sample households. While the household will be the final-stage sampling unit, individual household members will be included as target subjects for the variables needed.

However, for this particular proposal, or the PhilTiDeS arm of the survey for that matter, only a sub-sample population (about 25% of sampled households in one replicate) of non-pregnant/non-lactating adult population members aged 20 years old and over totalling about 5,000 subjects will be included, which will give at least, a national estimate.

Field Personnel Training

The Philippine Society of Endocrinology and the FNRI-DOST jointly conducted a series of training workshop for the field personnel. The workshop consisted of lectures on thyroid physiology, anatomy and thyroid disorders, hands on training on thyroid examination and practice survey using the PhilTiDeS questionnaire. (9,10) . Standardization and evaluation of inter-observer variability survey practicum was conducted in the outpatient thyroid clinics of the 4 PSEM accredited fellowship programs in endocrinology namely Philippine General Hospital, Makati Medical Center, University of Sto.Tomas and St. Luke’s Medical Center. The survey practicum was supervised by endocrinologists and endocrine fellows in training.

Study Population

Inclusion Criteria:

1. All adults residing in the Philippines 20 years old and over, non-pregnant and non-lactating

2. Willing to give informed consent

Exclusion Criteria:

1. Filipino but not residing in the Philippines

Data/Sample Collection and Laboratory Determination

Blood Collection: A trained registered medical technologist will do blood extraction by venipuncture after 10-12 hours of fasting. Serum samples will be stored frozen in the field in freezers or liquid nitrogen tanks and will be transported to FNRI in ice chest with dry ice for analysis of Free T4 and TSH in an accredited laboratory in Manila. Serum TSH concentration will be measured by a third generation (Chemoluminescent) procedure.

Data Organization, Processing and Analysis

Descriptive statistics (means, standard deviations, confidence intervals and medians for prevalence ) will be generated using Statistical Package for the Social Sciences (SPSS) program. Analysis of data will classify thyroid disorders according to presence or absence of goiter based on physical examination, thyoid disorder based on clinical symptomatology assessed through questionnaire correlated with biochemical FT4 and TSH determinations, iodine sufficiency assessed by urinary iodine and lipid levels.

Thyroid Function Biochemical Status will be classified as follows:

1. elevated TSH and low FT4 levels: overt hypothyroidism

2. low TSH and elevated FT4: overt hyperthyroidism

3. elevated TSH and normal FT4: subclinical hypothyroidism

4. low TSH and normal FT4: subclinical hyperthyroidism

Bibliography References:

1.Helfand M, Redfern C. Screening for Thyroid Disease :an update . Annal of Intern Med 129, 2, 144-158,1998

2 . Knudsen Nm Laurberg P, Perild H. Risk factors for goiter and thyroid nodule. Thyroid 12, 879-888, 2002

3. Knudsen N, Laurberg P, Rasmussen LB et al. Small differences in thyroid function may be important for body mass index and the occurrence of obesity in the population. Journal of clinical endocrinology and metabolism 90, 4019-24, 2005

4. Gumieniak O, Perlstein TH, Hopkins PN et al. Thyoird function and blood pressure homeostatis in euthyroid subjects. J Clin Endo and Metab, 89, 3455-61, 2004

5. Asvold BO, Bjoro T, Nilsen TI et al Association of blood pressure with TSH in the reference range a population based study. J clinic endo and metab 92, 841-45, 2007

6Teng W, Shan ZnTeng X et al. Effect of iodine intake on thyroid diseases in China. New Eng J of Med 29, 2783-2793, 2006

7.M.A. Tuazon and R.C.F. Habito. The National Salt Iodization Program in the Philippines.

8. Prevalence of Iodine Deficiency in the Philippines. .ph/nutriupdate/ nutriodine.htm

9.T. Bjuro, J Holmen, eKruEger, K Midthjell, K Hunstad, T Schreiner, L Sandnes and H Brochmann. Prevalence of thyroid disease, thyroid dysfunction and thyroid peroxidase antibodies in a large, unselected population. The health Study of Nord-Trundelag (HUNT). European Journal of endocrinology (2000) 143 639-647

10. Caceres et al. Philippine J Int Medicine 31: 253-260l Sep-Oct 1993.

Questions?

Can we publish the protocol ? we need consent of FNRI as stated in contract.

What is the title of caceres journal from which questionaaire was adapted?

Take our other references as they were not used in this write up?

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