1 Subclinical thyroid dysfunction and blood pressure: a community-based study John P. Walsh, Alexandra P. Bremner, Max K. Bulsara‡, Peter O’Leary, Peter J. Leedman, Peter Feddema and Valdo Michelangeli Clinical Endocrinology,2006;65:486–491

2 Background Thyroid hormone –Cardiovascular hemodynamics and function Overt hypothyroidism –Diastolic hypertension, atherosclerosis Overt hyperthyroidism –Cardiac output –Systemic vascular resistance

3 Population-based, longitudinal study 5888 adults aged 65 years or older Subclinical hyperthyroidism & hypothyroidism –non–statistically significant higher prevalence of hypertension JAMA. 2006;295:

4 Subclinical hypothyroid patients (n = 50) Diastolic blood pressure (DBP) & Brachial artery PWV –significantly higher in subclinical hypothyroid patients Increased pulse wave velocity in subclinical hypothyroidism J Clin Endocrinol Metab ;91:154-8

5 Purpose Subclinical thyroid dysfunction Blood pressure In the Busselton Thyroid Study Cohort

6 Methods The Busselton Health Study –a series of cross-sectional health surveys –Based on data from the 1981 survey In 2001, serum TSH, free thyroxine,thyroid peroxidase antibody(TPOAb) concentrations Exclusion –History of thyroid disease –Treatment for hypertension

7 Euthyroidism –TSH 0·4–4·0 mU/l regardless of free thyroxine concentration Subclinical hypothyroidism –TSH > 4·0 mU/l & normal free T4 TSH ≤ 10 mU/l TSH > 10 mU/l Subclinical hyperthyroidism –TSH < 0·4 mU/l & normal free T4 TSH < 0·1 mU/l TSH ≥0·1 mU/l but < 0·4 mU/l

8 Results 2033 study subjects : males -1051, females Mean age : 50 years (range 17–89 years) Subclinical hypothyroidism : 105 (5·2%) Subclinical hyperthyroidism : 35 (1·7%) Positive TPO antibodies : 225 (11·1 %) Correlation between TSH and SBP (P=0·04) No significant correlation between TSH and DBP (P= 0·25) After adjustment for age, age & sex –relationship between TSH and SBP  no longer significant

9 Table 1. Systolic and diastolic blood pressure analysed by categories of serum TSH concentration

10 Table 2. Systolic and diastolic blood pressure in subjects with subclinical thyroid dysfunction and in euthyroid subjects

11 Table 3. Odds ratios for hypertension (SBP = 140 mmHg, DBP = 90 mmHg or on treatment for hypertension) analysed by categories of serum TSH concentration

12 Table 4. Odds ratios for hypertension (SBP = 140 mmHg, DBP = 90 mmHg or on treatment for hypertension) in subjects with subclinical thyroid dysfunction compared with euthyroid subjects

13 Correlation between TPO antibody concentration and SBP or DBP –No significant Prevalence of SBP, DBP or hypertension between subjects with positive TPO antibodies and antibody- negative subjects –No significant

14 Discussion Population based survey in Germany A study population of 4087 subjects (2050 women) Subclinical Hyperthyroidism is not associated with hypertension Journal of Hypertension 2006, 24:1947–1953

15 The strengths of study –Community-based design and large sample size The limitations of study –Blood pressure : measured only once –Some participants : ‘white coat’ hypertension –Unable to exclude subjects on treatment such as glucocorticoids, amiodarone or lithium –Free T3 concentrations : not measured

16 Conclusion Between subclinical hypothyroidism and Hypertension  No associatoin Prevalence of hypertension –increased in subclinical hyperthyroidism