Is my thyroid making me fat?

Justin Moore, MD, FACPDivision Chief, Endocrinology and MetabolismMedical Director, Via Christi Weight Management

TRH: Thyrotropin-releasing hormone

TSH: Thyroid stimulating hormone

Growth rate?He said growth rate!

Only three things can go wrong with your thyroid

1. Underactive (“hypothyroidism”)2. Overactive (“hyperthyroidism”)3. Enlargement (“goiter”)/cancer

What drug was started 7-23-47?

080176

cite source for pic

Questions to answer1. How do we measure thyroid function?2. Do overweight or obese persons have different

thyroid blood tests than persons of normal body weight?

3. If such persons have low thyroid function, is treatment with thyroid hormone associated with a reduction in their weight?

4. Weight aside, what is the evidence that treatment of mild thyroid dysfunction affects well-being?

1. How do we measure thyroid function?

Justin Moore

This may need replaced with a simpler figure

TSH (compared to free T4) presents an “amplified” picture of thyroid status

2. Do overweight or obese persons have different thyroid blood tests than persons of normal body weight?

The TSH level rises with age

NHANES III, PMID: 11836274

Heavier people have higher TSH levels than lighter people

Arch Intern Med. 2008;168(6):587-592

As people gain weight, their TSH level rises

Arch Intern Med. 2008;168(6):587-592

But it’s not just heavier people who have weird thyroid labs. They are also different in people with anorexia!

In anorexia and obesity, normalization of weight normalizes thyroid labs

Arch Intern Med 2008;168:568-569.

Why? Fat affects your thyroid

3.If overweight or obese persons have low thyroid function, is treatment with thyroid hormone associated with a reduction in their weight?

Randomized controlled trialsMainstream medicine holds medications (or hormones) to a very high standard

Population with disease(n=100)

Placebo group(n=50)

Hormone group(n=50)

Outcome? Outcome?

Meta-analysis

The results of many randomized, controlled trials combined into one “super-study”

Kaptein E M et al. JCEM 2009;94:3663-3675

Effects of thyroid hormone therapy on weight loss during caloric deprivation of euthyroid obese subjects

4. Weight aside, what is the evidence that treatment of mild thyroid dysfunction affects well-being?

Why might you treat someone with mild hypothyroidism?

• Some studies do report improvements in some outcomes– Clearness of thought– Cholesterol– Heart function

• Thyroid hormone at appropriate doses is reasonably safe

• Thyroid hormone is cheap

Does giving thyroid hormone to people with mild (“subclinical” hypothyroidism) do any good?

• Villar HC et al. Thyroid hormone replacement for subclinical hypothyroidism. Cochrane Database 2007, PMID: 17636722

• Overview of methods: – Meta-analysis

• Funding and support:– Not stated

Cochrane review (17636722)

• Patients: 12 RCTs (n = 485, > 75% women) in adult outpatients with subclinical hypothyroidism and no severe illness

• Intervention: Triiodothyronine (T3), thyroxine (T4), or both. – Daily LT4 doses varied from 65 µg (4 trials) to 150 µg (1 trial)

• Comparison: Placebo (11 RCTs) or no treatment (1 RCT)• Outcome: Symptoms, mood, quality of life, cognitive

function, serum lipids, myocardial relaxation, adverse events

Results of Cochrane 2007, PMID 17636722

Results of Cochrane 2007, PMID 17636722• In 1 trial (n = 66), thyroid hormone replacement improved

thought clarity• Weighted mean difference 2.4, (95% CI 0.3 to 4.5, P = 0.03)

• Groups did not differ in any trial for:– Quality of life (2 trials)– Adverse effects (4 trials)

• Persons with a baseline LDL cholesterol level >155 mg/dl had improvement in their cholesterol levels

What about giving thyroid hormone to fatigued patients with normal thyroid studies? (BMJ 2001, PMID 11668132)Patients: 25 persons with symptoms of hypothyroidism, but

normal thyroid function testing, and 19 controlsIntervention: 100 ug levothyroxine once daily for 12 weeks, then

“crossover”Comparison: PlaceboOutcome: Thyroid function testing, measures of cognitive

function, tests of psychological and physical well-being

Results• Subjects showed a greater response to placebo than

to thyroid hormone in 3/15 measures of psychological well-being

• Healthy subjects had significantly lower scores for vitality when taking levothyroxine compared to placebo (60 + 17 vs. 73 + 16, p <0.01)

• Fatigued patients’ scores on psychological testing were no different on thyroid hormone versus placebo– Worse on visual reproduction testing

BMJ 2001, PMID 11668132

• Controls: no significant change in psychological measures with either thyroid hormone or placebo

• Conclusion: Thyroid hormone does not have a non-specific effect on wellbeing in persons without thyroid dysfunction

BMJ 2001, PMID 11668132

Is levothyroxine safe?

• Turner MR et al, Levothyroxine dose and risk of fractures in older adults: nested case-control study. BMJ. 2011 Apr 28;342. PMID: 21527461

• Overview of methods: – Nested case-control study

• Funding and support:– Canadian Institutes of Health Research

Turner MR, BMJ, PMID: 21527461

• Patients: Canadian patients 70 to 105 years of age

• Intervention: Thyroid hormone• Comparison: Controls not on thyroid

hormone• Outcome: Any fracture

Results of BMJ 2011, PMID 21527461• Levothyroxine use was associated with a higher risk of

fracture (adjusted OR=1.88%; 95% CI, 1.71-2.05)• Higher doses of levothyroxine were associated with higher

risk.

Does Thyroid Hormone Replacement Reduce Mortality?

• Razvi S et al. Levothyroxine Treatment of Subclinical Hypothyroidism, Fatal and Nonfatal Cardiovascular Events, and Mortality. Arch Intern Med. Published online April 23, 2012. PMID: 22529180

• Overview of methods: Cohort study • Funding:

– Medical Research Council

PMID: 22529180

• Patients: Persons aged 40-70 or >70 years with subclinical hypothyroidism

• Intervention: Levothyroxine• Comparison: No treatment• Outcome: Ischemic heart events

Results of PMID: 22529180

• Younger patients (40-70) treated with thyroid hormone:– Multivariate-adjusted HR 0.61 (95% CI, 0.39-0.95)

• Older patients (>70) treated with thyroid hormone:– HR 0.99; 95% CI, 0.59-1.33

Be careful what doctors promise you…

Conclusions• Your thyroid gland is important, and affects almost

every organ system you possess• Hypothyroidism is common, but not nearly as

common as overweight or obesity• Thyroid function testing is easily obtained, and the

TSH blood test is adequate in more than 99 percent of people

Conclusions• Overweight or obese persons have different thyroid

blood tests than persons of normal body weight, but treating them for these test abnormalities does not typically promote weight loss

• Treatment of mild thyroid testing abnormalities has, at best, very mild effects on well-being, but is worth discussing with your doctor

Questions?

jmoore7@kumc.edu

KU-WichitaEndocrinology

@KUEndocrinology

Photo Credits

• Chicken and cat: http://community.breastcancer.org/forum/102/topic/765586?page=147• Pituitary gland: http://en.wikipedia.org/wiki/File:Pituitary_gland.png• Thyroid gland: http://en.wikipedia.org/wiki/File:Thyroid_gland.jpg• Butterfly neck: http://www.hannahweptsarahlaughed.com/2010/06/thyroid-update-butterfly-in-my-neck• Archie Cochrane: Cardiff University Library, Cochrane Archive, University Hospital Llandough• Iodized salt logo: http://en.wikipedia.org/wiki/File:Global_iodized_salt_logo.jpg• Goiter belt: http://www4.uwsp.edu/geo/faculty/ozsvath/images/goiter_belt.htm• John Brinkley: http://en.wikipedia.org/wiki/John_R._Brinkley