Subclinical Hypothyroidism & Metabolic Disease Michael D. Loughner, M.D. Endocrinology Associates, Denver, CO 303-722-4683 (p), 303-778-0726 (fax) May 2010

Subclinical Hypothyroidism (SCH) • AKA “Mild Thyroid Failure”

Prevalence of SCH • Adults: – Women: 8% – Men: 4%

• > age 60: – Women: 15% – Men: 8%

Etiology of SCH • Autoimmune (Hashimoto’s) Thyroiditis • Persistent TSH elevation in subacute thyroiditis, postpartum thyroiditis, painless thyroiditis • Drugs: amiodarone, lithium, etc. • Thyroid injury: surgery, radiation • Infiltrative disease (sarcoidosis, hemochromatosis, etc.)

SCH: When To Treat?

Natural History of SCH Initial TSH

Normalization (TSH 20 mIU/L or low free T4)

Overt Hypothyroidism

5-9.9 mIU/L

52%

6%

10-14.9 mIU/L

13%

40%

15-19.9 mIU/L

5%

86%

p 5.1 mIU/L and normal T4)

SCH Euthyroid

Total Chol*

LDL*

HDL

Trig

(mg/dl)

(mg/dl)

(mg/dl)

(mg/dl)

224

146

53

156

216

140

51

147

* p < 0.003

Arch Intern Med. 2000 Feb 28; 160(4):526-34.

Elevated Total and LDL Cholesterol in SCH • 2108 participants from community health survey in Australia

SCH Euthyroid

Total Chol*

LDL*

(mg/dl)

(mg/dl)

244

159

224

135

* p < 0.003

No difference seen in mean HDL or triglyceride levels

Clin Endocrinol (Oxf). 2005 Dec;63(6):670-5.

Altered Lipids Across TSH Reference Range • Cross-sectional population-based study of 30,656 subjects without known thyroid disease in Norway – Demonstrated that increasing TSH levels across the reference range (0.2-4.5 mIU/L) were linearly associated with deranged lipid concentrations p 240 mg/dl

Thyroid. 2007 Nov;17(11):1075-84.

Thyroid Function Associated with Metabolic Syndrome • Roos et al.: Cross-sectional cohort study of 2703 subjects – Both free T4 and TSH significantly associated with HOMA-IR (p