• T4 tetreiodothyronine (thyroxine)
• T3 triiodothyronine

• Tyrosine
• Iodine (100-150 mcg/day)

--come together to make mono- and di- iodothyronine

--those complex to make T3 and T4

--It has a negative feedback inhibition of the pituitary by.

--Serum thyroid hormone concentrations inhibit relseas of TRH (thyotropin releasing hormone) and TSH (thyroid stimulating hormone aka thyrotropin)

1. infertility
2. menstrual irregularities
3. depression

What are the serum [TSH] cutoffs for the following?

1. Overt HYPOthyroidism
2. Overt HYPERthyroidism
3. Subclinical HYPOthyroidism
4. Subclinical HYPERthyroidism

1. >10     mU/L
2. <0.2    mU/L
3. 4-10     mU/L
4. 0.4-0.2 mU/L

Normal range for TSH is 0.4-4 mU/L 

Types of tests to screen for Thyroid problems:

1. TSH concentration
2. TRH 
3. T4 and T3
4. Radio active iodine uptake test
5. antithyroglobin antibody test

What is the drug treatment of choice for HYPOthyroidism?

And Why?

Levothyroxine

• hormone content is stable and predictable
• daily dosing
• lack of allerginic factor

Levothyroxine

(dosing basics)

• Based on age and duration of problem
• <50 or those only having this a few months      100-125 mcg/day
• >50 yoa  (25-50 mcg/day)

*Lower in older patients b/c of possible MI/Angina*

Levothyroxine

(monitoring)

• Initiate treatment
• monitor clinical s/s in 2-3 wks including angina
• Repeat TSH and FT4 in 6-8 wks(norm/abnorm)
• normal--monitor TSH 3-6 mo for 1 year then yearly
• Abnormal--adjust dose, re-check in 6-8wks and repeat TSH in 6-8 wks

Can the patient switch betwen brands of levothyroxine?

• End stage of long-standing, uncorrected hypothyroidism associated with acute decompensation(unable to maintain critical body funcitons)

Myxedema Crisis

(treatment)

• Maintain adequate ventilation, BP, body temp, and blood glucose.
• IV thyroxine till oral therapy is abel to begin

**make sure to restart oral therapy**

• induced tachycardia
• Propranolol

1. Antithyroid drugs
2. Ablation therapy (radio active iodine)
3. Surgery
4. Lifestyle measures

• The thyroid takes up the radioactive iodine which iradiates the thyroid and induces necrosis to destoy the gland
• I131
• makes sure to stop antithyroid drugs 4-10 days before given I131

Thioamides:

• propylthiouracil (PTU)---BID dosing
• methimazol (MMI)-------daily dosing

MOA: competes with tyrosine molecules for oxidized iodine resulting in inhibition of organification and iodotyrosin coupling

Antithyroid Drugs

(monitoring)

• Clinical S/S
• TSH, FT4, FT3--every 6-8 wks until euthyroid state is achieved

• a rare but often medical emergency resulting from untreated hyperthyroidism.
• Propranolol gold standard for HR management

Potassium Iodide

(when to use)

• initiated 1-2 hrs after the first dose of PTU