Hypothrodism Flashcards
whats a Myxedema Coma?
Life threatening condition
Mortality of 60-70%
Usually in patients with severe and long standing hypothyroidism which markedly worsens.
Presentation of Myxedema Coma?
Progressive stupor/coma
Seizures
How to treat Myxedema Coma?
Intravenous levothyroxine and/or liothyronine as well as pharmacologic doses of glucocorticoids
Intravenous levothyroxine 400-500 (micro)g should be given initially***
Why should we treat Congenital Hypothyroidism?
FT4 & TSH screening on all births
Cretinism approximately 1 in 5000 births
Aggressive therapy within 45 days of birth
IQ improvement
How do we treat newborns for Hypothyroidism?
Newborn dose: 10-17 mcg/kg/day (10x more than adults)
–empty stomach
Lifetime replacement
how do we treat Treatment of Subclinical Hypothyroidism?
Start with 0.025-0.050 mg/day
Elevated cholesterol - HYPO
TSH >5 but <10 mIU/L, normal FT4
Consider levothyroxine replacement if:
Nonspecific or subtle symptoms
Mild fatigue, lethargy
How do we treat elderly for Hypothyroidism?
Elderly patients and patients with a history of cardiac disease. Age >65—NEED LOWER DOSE OF LEVOTHYROXINE*
Elderly have an age-related decrease in thyroxine slower rates.
Usually 0.0125-0.025 mg (or 12.5 mcg-25mcg) daily to start. Start low, go slow
How do we treat preangn women with Hypothyroidism?
May need to increase dose up to 50% in regular pregnancy.
Pregnancy – NEED MORE LEVOTHYROXINE
TSH/FT4 always checked in the first trimester
Most patients will require a 45% (range 20-50%) increase in their baseline levothyroxine dosage
Recheck TSH/FT4 6-8 weeks postpartum
The levothyroxine dosage should return to the prepregnancy dose immediately after delivery
whats the used Levothyroxine Use in Thyroid Cancer Management?
Sorry Marcus its Late
The growth and spread of thyroid carcinoma are stimulated by TSH.-Push Spread of Tumor
An important component of thyroid carcinoma management is the use of LT4 to suppress TSH secretion
Early in therapy, patients receive the lowest LT4 dose sufficient to fully suppress TSH to undetectable levels.
Controlled trials show that suppressive LT4 therapy reduces tumor growth and improves survival.
These patients are purposefully “overtreated” with LT4, sometimes to a fully-suppressed TSH level, and rendered subclinically hyperthyroid
Levothyroxine/Warfarin Interaction: what should we do?
Enhanced anticoagulant activity
Monitoring is essential
Monitoring INR,s/s of Increased Bleeding.
Hypothyroid patients will catabolize Vitamin K
dependent clotting factors SLOWLY** therefore decreased anticoagulant effect.
With T4 replacement the anticoagulant effect will increase.
what are the Factors Effecting Successful Levothyroxine Therapy?
Bile acid binders Calcium H2 blockers Oral bisphosphonates Phosphate binders (sevelamer, aluminum) Proton pump inhibitors Soy Sucralfate
Levothyroxine on Empty stomach is very important
Decreased TBG – Higher # of FT4 Cirrhosis Estrogen therapy Fluorouracil Methadone Mitotane Pregnancy Tamoxifen Raloxifene
Increased TBG-Lower # of FT4 Androgens Asparaginase Corticosteroids Niacin (sustained-release)
TBG-Thyroxine-binding globulin
what are the Risks of Poorly Managed Levothyroxine Therapy?
Overtreatment
Depression
Mental status changes
Osteoporosis
Fractures
what are the Risks of Poorly Managed Levothyroxine Therapy?
Undertreatment
Depression
Mental status changes
Levothyroxine details?
Average replacement dosages of 1.6 g/kg/day (100 g) are sufficient to normalize TSH.
Clinically recommend PO to IV dosage reduction of 50%.
Bioavailability issues between products
Baseline correction method (Endogenous T4)
AB1, AB2, AB3, AB4-Bioequivant subheadings, AB1=AB1 and AB1≠AB2. There will be TSH changes if playing with dosage forms.
USE THE SAME PRODUCT CONSISTENTLY
Evaluate TSH/FT4 in 6-8 weeks after initiation, dosage changes or product changes.
Therapeutic equivalence more important then bioequivalence
wt kg x 1.6 (micro)g/kg/day = daily dose.
Round to the nearest tablet dosage.
Take on an empty stomach.
Check TSH, FT4 in 6-8 weeks.
May increase dosage by 12.5 to 25 (micro)g/day monthly with a goal of normalizing TSH/FT4.
Continue levothyroxine dosage for lifetime replacement.
When normalized recheck TSH/FT4 every 6 to 12 months.
Overt Hypothyroidism
Overt Hypothyroidism
> 10 mIU/L - TSH
<0.9 ng/dL -FT4
Mild/Subclinical Hypothyroidism
5-10 mIU/L -TSH
Normal -FT4
Thyroid Hormones
Desiccated Thyroid:
Unpredictable, stability?, allergic reactions.
Liothyronine (Cytomel® ):
Synthetic T3, multiple daily dosing.
Liotrix (Euthyroid ®, Thyrolar® ):
T4 to T3 in a 4:1 ratio, expensive –no therapeutic logic
Levothyroxine (T4): Drug of choice for thyroid replacement therapy. Chemically stable. Inexpensive Free of antigenicity. Uniform potency
Liotrix
Euthyroid ®, Thyrolar
Liothyronine
Cytomel
Desiccated Thyroid:
Not stable -don’t worry
Hypothyroidism Presentation
Dry, coarse skin & hair Cold intolerance Weight gain Slow, hoarse speech Lethargy Fatigue
Drug-Induced Hypothyroidism
Amiodarone-induced hypothyroidism is more common in iodine-sufficient areas.
Amiodarone-induced hyperthyroidism is more common in iodine-deficient areas.
Releases 6 mg of free iodine daily which is 20-40 times the average daily intake of iodine
Lithium
Inhibits thyroid hormone synthesis and secretion
May require LT4 therapy.
Interferon-α
Hypothyroidism in up to 39% of patients treated for Hepatitis C.
Tyrosine kinase inhibitors
=Sorafenib (Nexavar®), Sunitinib (Sutent®),
Imatinib (Gleevec®)
-Four-fold increase in TSH in patients treated for thyroid cancer.
-Can cause a mild hyperthyroidism followed by hypothyroidism.
Secondary Hypothyroidism:Pituitary Disease: (TSH)
Pituitary insufficiency may be caused by destruction of the pituitary gland by pituitary tumors or external pituitary radiation
Secondary Hypothyroidism: Hypothalamic Hypothyroidism: (TRH
In adults and children it may be due to cranial irradiation, trauma, neoplastic disease.
Predominantly in children
Iatrogenic Hypothyroidism
Follows exposure to radiation (radioiodine or external radiation) or surgery.
Patients who have a total thyroidectomy will be hypothyroid in 1 month.
Iodine deficiency
Rare in adults, rare in the United States
Causes of Hypothyroidism?
Primary Hypothyroidism
Autoimmune thyroiditis (Hashimoto’s disease)
Iatrogenic (irradiation, surgery)
Iodine deficiency
Drugs (amiodarone, radiocontrast media, lithium, interferon-α, tyrosine kinase inhibitors)
Secondary Hypothyroidism
Pituitary disease
Hypothalamic disease
Whats the most frequent cause of hypothrydism?
Hashimoto’s Thyroiditis (Autoimmune Thyroiditis)
Most frequent cause of hypothyroidism
