Thyroid Disease Facts

Thyroid Disease Facts
By:Jeffrey Medland
Lt Col, USAF, MC, SFS
Chief, Endocrinology
MGMC, Andrews AFB, MD
Capital Conference-June 2007

Outline
* Thyroid Testing
* Hypothyroidism
o Causes
o Signs/symptoms
o Treatment
* Hyperthyroidism
o Causes
o Signs/symptoms
o Treatment
* Thyroid Nodules/ Cancer
* Thyroid Disease and Pregnancy
o Hypothyroidism
o Hyperthyroidism (Hyperemesis Gravidarum, Graves’)
o Thyroiditis
* Factors affecting Thyroid function, LT4

Thyroid
Colloid
Apical Membrane
Basal Membrane
Thyroid Peroxidase (TPO)
“Iodination Reaction”
“Coupling Reaction”

Thyroid Testing
* TSH
o Best test for screening for thyroid dysfunction!
o Log/linear response w/ FT4
+ A 2-fold change in FT4 produces a 100-fold change in TSH
o Not specific for a particular thyroid disease.
+ Don’t use TSH alone for diagnosis!
o Also useful in
+ Assessing LT4 tx in 1° hypothyroidism
+ Monitoring TSH-suppressive tx in thyroid Ca
* FT4
o Testing methods:
+ Equilibrium dialysis
+ Analog assays
o Abnormal TSH check this next
o Indications:
+ In conjunction w/ TSH for diagnosing hyperthyroidism or hypothyroidism.
+ Monitoring LT4 replacement in central hypothyroidism (TSH not helpful)
+ Assessing response to tx following 131-RAIA (Graves, toxic nodules)
+ Monitoring ATD tx in pregnant females
* FT3
o Abnormal TSH + normal FT4, then check this (T3 Thyrotoxicosis)

Pituitary Hypothyroidism
Subclinical Hyperthyroidism, Autonomous nodules
Thyrotoxicosis, Thyroiditis (stage 1)
Pituitary Hyperthyroidism
Subclinical Hypothyroidism
Primary Hypothyroidism, Thyroiditis (stage 3)
Clinical Status
FT4
Overview of Thyroid Function Tests
* Thyroid Antibodies (TPO, Tg, TSI, TRAb)
* Thyroglobulin (Tg)
* Radioactive Iodine Uptake and Scan (RAIU/Scan)
* Tc99m-Pertechnetate Scan
* Fine Needle Aspiration (FNA)
* Ultrasound
* Calcitonin

Hypothyroidism
Thyroiditis
Hypothyroidism (Treatment)
Hypothyroidism (treatment in general)
Indications for LT4 replacement
Hypothyroidism + surgery
Hypothyroidism + elderly
Combined LT4/LT3 tx
Hyperthyroid Eye Disease
Does131-RAIA worse ophthalmopathy?
Graves’ Dermopathy Thyroid Dermopathy
Thyroid Acropachy
RAIU/Scan
Increased RAIU
Decreased RAIU
Surgery (sub-total thyroidectomy)
Apathetic Hyperthyroidism
Thyroid Storm
Subclinical Hyperthyroidism
Thyroid Nodules
Red Flags concerning for Cancer
FNA Results:
Thyroid Nodules “Mimickers”
Thyroid Cancer
MTC
Thyroid Disease in Pregnancy
Four factors alter thyroid function in pregnancy
1) Transient ↑ in hCG, during the 1st trimester can stimulate the TSH-R
2) E2-induced ↑ in TBG during the 1st trimester, which is sustained during pregnancy.
3) Alterations in immune function leading to onset, exacerbation, or amelioration of an underlying autoimmune thyroid disease.
4) urinary iodide excretion, which can cause impaired thyroid hormone production in areas of marginal iodine deficiency (<50 µg/d).
Known Hypothyroidism already on LT4
Stage 1 to 4
Hyperemesis Gravidarum (HG)
Hyperemesis Gravidarum vs. Graves’
Causes of Increased LT4 requirement
Drugs Affecting Thyroid Function
Somatostatin, Glucocorticoids
Dopamine
Amiodarone Effect on Thyroid Function
Amiodarone and the Thyroid
Iodine Effect
Direct Toxic Effect
* Thyroiditis (AIT type 2)
“Innocent Changes”
Jod-Basedow phenomenon (Historical)
* Definition- Hyperthyroidism induced by excess Iodine.
* Coindet (French physician) in 1821 published his cases about Hyperthyroidism.
* In the English speaking world this became known as Graves’ disease (1835), and in the German speaking world as von Basedow’s disease (1840).
* Coindet’s cases of hyperthyroidism were actually Iodine-induced, hence it came to be known as the Iodine-Basedow phenom.
* Jod is German for Iodine, hence the Jod-Basedow phenom!
* Coindet was deprived of credit for not only describing Hyper- thyroidism, but also the variant of hyperthyroidism caused by excess Iodine
* The credit was given to Dr “Jod” who never existed!

Conditions affecting Thyroid Function
Autoimmune Polyglandular Syndromes 2
Hypokalemic Periodic Paralysis
Hyperthyroid Eye Disease
Cutis Aplasia
Cutis Aplasia Keloid
Cutis Aplasia
Thyroid Binding Globulin (TBG)
Increased TBG
Decreased TBG
Thyroid Regulation
Amiodarone the Thyroid
Amiodarone Effects on Thyroid
Thyroid Hormone
* There is no absorption from the stomach. Absorption occurs in the small bowel.
* The main absorptive sites appear to be the proximal and mid-jejunum.
* Progressively decreasing degrees of absorption occur along the distal bowel and proximal colon.
* Hypothyroidism can lead to a slight increase in absorption.

Thyroid Disease Facts.ppt