Thyroid & Hypothyroid (week 3) Flashcards
Overt Hypothyroidism
Diagnosis:
TSH > 10,
fT4 reduced or low-normal with symptoms
Adult Hypothyroidism causes?
- Generalized slowing of the metabolic rate
* About 25% of metabolism is ran by the thyroid
The incidence of hypothyroidism has a female to male ratio?
- The incidence of hypothyroidism has a female to male ratio of 10:1
- Hypothyroidism, including “subclinical” hypothyroidism, is estimated to affect 10-20% of women over the age of fifty
Most common cause of hypothyroidism?
(Autoimmune)
Outside the USA?
Secondary and Tertiary Hypothyroidism?
Functional (protective) or Pathological
Hashimoto’s thyroiditis (autoimmune hypothyroidism)
**Iodine deficiency
**Pituitary or hypothalamic causes)
**Can decrease function bc adapting
Hypothyroid Presentation
Symptoms:
Symptoms:
- Fatigue/Low energy
- “Mental fog”
- Muscle weakness
- Constipation
- Weight gain
- Cold intolerance
Hypothyroid Presentation
Signs:
Signs:
- Delayed relaxation phase of DTRs
- Goiter (may or may not be present)
- Lateral thinning of eyebrows
- Myxedema
Lab Diagnosis of Hypothyroidism:
- Elevated: TSH
(7-10 CVD & sx’s under 70yo)
(Normal range .5-10) - Low: free T4 and free T3
- Elevated:
A. anti-TPO (95% of patients)–>Also seeing in Grave’s Dz but more common in Hashimoto’s)B. anti-TG (60% of patients) - Elevated: ESR or CRP in subacute thyroiditis (De Quervain’s thyroiditis)
- Elevated: thyroglobulin in destructive thyroiditis (and thyroid cancer)
Hypothyroid Management:
- Levothyroxine: synthetic T4, considered first line therapy as 80% of Levothyroxine
- Lifestyle, Dietary, and Herbal support
*Supplemental support -
Selenium: 200mcg/day may (Shows a Dec. of Auto a/b’s)
(Autoimmune can self resolve!!!)
First line therapy – overt hypothyroidism:
Levothyroxine (T4) initiation:
Healthy adults – 100-125 mcg/day
> 50 yo w/o CV disease – 50mcg/day
> 50 yo with CV disease – 12.5-25mcg/day
COMBO T4/T3->when pt’s don’t feel any better after Levo, but can give hyperthyroid….
***Glandular can up regulate TPO a/b’s.
Monitoring Levothyroxine:
(More compliant at night & works better)
(Coffee may decrease absorption)
(Metformin drops TSH levels)
Monitor TSH 4-8 weeks after initiation of Levothyroxine, and every 4-8 weeks until you achieve stable normal TSH values. Once stable check after 6 months and then yearly.
Symptoms should improve after 2 weeks (patients usually report sooner) yet it can take up to 6 weeks for TSH to normalize with treatment.
Natural Treatment for Hypothyroidism In a research study…
- 10 OTC supplements tested “thyroid support”
* 9/10 had T3, 5/10 had T4, 5/10 did not list animal thyroid tissue
Affects of Excess Iodine on Thyroid Hormone Production
Wolff-Chaikoff effect:
Inhibition of thyroid hormone production by iodine.
Affects of Excess Iodine on Thyroid Hormone Production
Jodbasedow effect:
Induction of thyrotoxicosis by iodine.
Affects of Excess Iodine on Thyroid Hormone Production
Autoimmune thyroid disease
Iodides may induce thyroid autoantibodies that cause hypothyroidism (Hashimoto’s thyroiditis) or hyperthyroidism (Graves’ disease).
Levothyroxine (T4) Absorption:
Absorption rates vary significantly (40-80%)
Absorption rates are higher with protein binding, and decrease with coffee, soy, walnut, fiber, iron, and magnesium ingestion within one hour of taking T4
Remind patients not to drink coffee with morning dose!
What Affects Levothyroxine?*
- Decreases hepatic metabolism
Metformin (possibly)
2. Inhibition of 5’ deiodinase Propranolol Iodine PTU, Methimazole Glucocorticoids
- Increases thyroid binding globulin levels
Estrogen
Methadone - Decreases thyroid binding globulin levels
Androgens
Glucocorticoids
Nicotinic acid
Thyroid Hormone Warnings:
Thyroid hormones should be used cautiously with:
- Cardiovascular disease (arrhythmias, CAD, tachycardia)
- Adrenal insufficiency
- Diabetes mellitus
- Low T3 syndrome
- Older patients
Hypothyroid Prognosis:
Hypothyroidism over age 85 associated with…
*Lower mortality over 4 years.
Hypothyroidism over age 85 associated with lower mortality over 4 years.
(JAMA 2005 Mar 23;293(12):1447)
Subclinical hypothyroidism 40% likely to progress to overt hypothyroidism
(N Engl J Med 2001 Jul 26;345(4):260)
Common spontaneous resolution with no intervention within 1-5 years
(J Clin Endocrinol Metab 2005 Jul;90(7):4124)
In subclinical hypothyroidism TSH elevation correlated with increased CVD risk
(JAMA 2010 Sep 22;304(12):1365)
Hypothyroid Prognosis:
Life threatening complications
Overt Hypothyrodisim: myxedema coma.
Loss of consciousness and life-threatening low body temperature.
- Low social economic standing
- No heat in winter
Subclinical Hypothyroidism
- Thyroid function is only mildly low,
- T4 normal
- TSH elevated,
- Increased risk of coronary heart disease, especially if TSH >10 mU/L
CVD benefits <75 yo under 10
CVD benefits >75 yo over 10
Hashimoto’s Presentation
Risks:
Sx’s:
Signs:
*Risk:
Strong family history – dominant gene
*Symptoms:
Either hypo/hyper thyroid symptoms
Goiter and neck tightness
*Signs:
Goiter (may or may not be present)
Hyper or hypo
Hashimoto’s and Celiac?
Both common autoimmune diseases, so often found together
CD may predispose individuals to develop autoimmune thyroid disease
Thyroid disease is often diagnosed before CD
Check for gluten sensitivity or avoid gluten in the diet with all autoimmune thyroid pts.
FMHX is at higher risk
Hashimoto’s Management:
First line therapy: Levothyroxine initiation ( same as before) Healthy adults – 100-125 mcg/day > 50 yo w/o CV disease – 50mcg/day > 50 yo with CV disease – 12.5-25mcg/day
Second line therapies Iodine restriction (<100mcg/d X 3 months) (Yonsei Med J 2003 Apr 30;44(2):227) Selenium – 200mcg daily (Thyroid 2010 Oct;20(10):1163)
Hashimoto’s Prognosis:
Rate of progression from Hashimoto’s to hypothyroidism is about 25% per year in patients with elevated antibodies
In about 25% of adults diagnosed with Hashimoto’s will be able to discontinue medication after 1 year and maintain euthyroid
(N Engl J Med. 1996 Jul 11;335(2):99-107)
