Download THYROID DISORDERS

THYROID DISORDERS
-Euthyroid Goiter
-Euthyroid sick syndrome
-Hyperthyroidsm
-Hypothyroidism
-Thyroiditis
-Thyroid cancers
SYNTHESIS AND RELEASE OF THYROID
HORMONES
IODIDE (food, water)  concentrated in thyroid gland 
ORGANIC IODIDE
TYROSINE IN INTRAFOLLICULAR
THYROGLOBULIN 
IODINATED TO MONOIODOTYROSINE AND
DIIODOTYROSINE 
2+2= TETRAIODOTHTYRONINE (THYROXINE, T4)
or 2+1=TRIIODOTHYRONINE (T3)
Lysosomes containing proteases cleave T3 and T4 from
thyroglobulin  free T3 free T4
Blood stream: TBG (thyroxin binding globulin), TB prealbumin, in equilibrium with free hormones
Only free T3 and T4 available to peripheral tissues
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Formation of T3 and T4 regulated by TSH (Thyrotropin)
mediated by cAMP, with negative feedback mechanism by
free T3 and T4
T3 is the metabolically active hormone
TSH secretion also influenced by TRH
EFFECTS OF THYROID HORMONES
1) increase protein synthesis (intracellular T3 influences
formation of mRNA)
2) T3 increases O2 consumption y increaing activity of
Na+,K+ -ATPase
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LABORATORY TESTING OF THYROID
FUNCTION
1- MEASUREMENT OF SERUM TSH
- Normal: rules out thyroid dysfunction
- Suppressed with normal T3,T4: subclinical
Hyperthyroidism
- Elevated with normal T3,T4: subclinical
Hypothyroidism
Higher sensitivity of second generation immunometric
essays.
2 -MEASUREMENT OF TOTAL SERUM T4
- changes in serum-binding protein levels produces
changes in T4 (INCREASE: pregnancy, estrogen
therapy, oral contraceptives, infectious hepatitis,
DECREASE: anabolic steroids, corticosteroids, large
doses of phentoin and aspirin displace T4 from binding
sites)
3 - MEASUREMENT OF FREE T4
-avoids pitfalls due to changes in protein levels
4- MEASUREMENT OF TOTAL SERUM T3 AND FREE
T3
As for T4
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5- TESTING WITH TRH
- to distinguish between pituitary and hypothalamic
hypothyroidism
- in hyperthyroidism TSH release remains suppressed
- currently rarely needed
6- MEASUREMENT OF THYROID
AUTOANTIBODIES.
- AB to thyroid peroxidase and thyroglobulin in
Hashimoto's thyroiditis
- AB to thyroid peroxidase in Graves' disease (Ab against
TSH receptor on thyroid follicular cell TRAb)
- Thyroid stimulating antibody assay
- Antibodies against T4 and T3 in patients with
autoimmune thyroid disease
7. MEASUREMENT OF THYROGLOBULIN
IN patients after thyroidectomy for cancer: indicates
residual normal or malignant thyroid tissue in patients
receiving TSH suppressive doses of l-thyroxine
8- TESTING FOR RADIOACTIVE IODINE UPTAKE
I 123
Differential diagnosis of hyperthyroidism
9 - SCANNING OF THE THYROID
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with radioidine or technetium-99m
Evaluation of structural abnormalities and nodular thyroid
disease (hot vs cold nodule)
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EUTHYROID GOITER
An enlargement of the thyroid gland without clinical or
laboratory evidence of thyroid dysfunction unless the
etiology is iodine deficiency (endemic [colloid] goiter)
EUTHYROID SICK SYNDROME
A syndrome characterized by abnormal thyroid function
tests in clinically euthyroid patients suffering from severe
non-thyroidal systemic illness
HYPERTHYROIDISM (Thyrotoxicosis)
A clinical condition encompassing several specific diseases,
characterised by hypermetabolism and elevated serum
levels of free thyroid hormones.
- Graves' disease (diffuse toxic goiter)
- Inapprorpiate TSH secretion
- Molar pregnancy, choriocarcinoma and hyperemesis
gravidarum
- Toxic solitary or multinodular goiter (Plummer's disease)
- Nonautoimmune autosomal dominant hyperthyroidism
- Lithium-induced goiter
- Thyroiditis
- Thyrotoxicosis factitia
- Iodine ingestion
- Metastatic thyroid cancer
- Struma ovarii
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SUBCLINICAL HYPERTHYROIDISM
No symptoms or minimal symptoms of hyperthyroidism
with normal serum FT3 and FT4 amd low serum TSH
HYPOTHYROIDISM (Mixedema)
The characteristic clinical response to thyroid hormone
deficiency in the adult.
- Primary Hypothyroidism
- Secondary hypothyroidism
SUBCLINICAL HYPOTHYROIDISM
Either no symptoms or minimal symptoms suggestive of
hypothyroidism with normal serum T4 and T3 and elevated
TSH concentrations
THYROIDITIS
- Silent lymphocytic thyroiditis (a subacute disorder
occurring most commonly in women in the postpartum
period)
- Subacute thyroiditis (An acute inflammatory disease of
th ethyroid probably caused by a virus)
- Hashimto's thyroiditis (autoimmune thyroiditis) (A
chronic inflammation of the htyroid with lymphocitic
infiltration of the gland caused by autoimmune factors)
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THYROID CANCERS
Suspicion:
age (young)
sex (male)
solitary nodule
cold nodule
history of radiation exposure
radiograohic evidence of fine stippled (papillary) or dense
homogeneous (medullary) calcifications
recent or rapid enlargement
stony-hard consistency
- PAPILLARY CARCINOMA (60-70%)
Female/male 3/1
Spreads by the lymphatic system
Well differentiated, TSH dependent
- FOLLICULAR CARCINOMA (15%)
elderly
blood spreading
- ANAPLASTIC CARCINOMA (10%)
Death within 1 year
- MEDULLARY CARCINOMA
Sporadic or familial
- UNDIFFIERNTIATED THYROID CANCER
- RADIATION INDUCED THYROID CANCER
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