Thyroid Flashcards
Radio iodine uptake
Enlarged gland with increased tracer uptake that is distributed homogenously
GRAVES DISEASE
Radio iodine uptake
Focal areas of increased uptake with suppressed tracer uptake in the remainder of the gland
TOXIC ADENOMAS
Radio iodine uptake
Gland is enlarged with distorted architecture with multiple areas of relatively increased or decreased tracer uptake
TOXIC MNG
Radio iodine uptake
Very low Radio iodine uptake due to follicular cell damage and TSH suppression
SUBACUTE, VIRAL AND POSTPARTUM THYROIDITIS
Radio iodine uptake
Thyrotoxicosis factitia
Associated with low uptake
Thyroid scintigraphy
Functioning or hot nodules
Are they benign or malignant?
Almost never malignant
Recommended average daily intake of iodine
Adults
150-250 ug/day
Recommended average daily intake of iodine
Children
90-120 ug/day
Recommended average daily intake of iodine
Pregnant and lactating women
250 ug/day
This protein binds 80% of the thyroid hormones
Thyroid hormone binding globulin
Albumin bunds
10% T4 and
30% T3
Deficiency of this mineral may contribute to neurologic manifestations of cretinism
Selenium
These drugs suppress TSH
Dopamine
Glucocorticoids
Somatostatin
Time for TSH secretion after TRH secretion
15 mins
This is characterized by:
- Defective organification of iodine
- Goiter
- Sensorineural deafness
Pendred syndrome
There is marked lymphocytic infiltration of the thyroid with germinal center formation
- atrophy of the thyroid follicles
- oxtail metaplasia
- absence of the colloid
- mild to moderate fibrosis
Hashimoto’s thyroiditis
Extensive fibrosis, lymphocytic infiltration less pronounced, thyroid follicles completely absent
This represents the end stage of Hashimotos thyroiditis
Atrophic thyroiditis
Account for 50% of
Genetic disease associated with autoimmune hypothyroidism
- HLA DR polymorphisms
HLA DR3, DR4, DR5
2.!CTLA4, a T cell regulatory gene
Composition of thyroid lymphoid infiltrate in autoimmune hypothyroidism
Which PRIMARILY MEDIATES thyroid cell destruction
Activated CD4 and CD8 T cells
B cells
CD8 T cells mediate thyroid cell destruction by
1) performing induced cell necrosis
2) granzyme B induced apoptosis
Mechanism of myxedema in hypothyroidism
Increased dermal glucosamine glycol content traps water giving rise to skin thickening without pitching
Steroid responsive syndrome associated with TpO antibodies
Myoclonus
Slow wave activity on EEG
Hashimotos encephalopathy
Signs and symptoms of other autoimmune disease
Which may be found in autoimmune hypothyroidism
Celiac disease Dermatitis herpetiformis Chronic active hepatitis Rheumatoid arthritis Systemic lupus erythematosus Myasthenia Garcia Sjögren's syndrome
% of patients with autoimmune hypothyroidism where thyroid associated ophthalmopathy is found
5%
Goal of treatment in secondary hypothyroidism
Maintain T4 levels in the upper half of the reference range
Replacement dose of levothyroxine if there is no residual thyroid function
1.6 ug/kg body weight
(100-159 ug)
Taken 30 mins before breakfast
TSH monitoring once full replacement is achieved
2-3 yrs
Patient missed a dose levothyroxin e
Skip dose
Or double dose?
Double dose. T4 has a long half life
When to treat sub clinical hypothyroidism
TSH levels above 10 mIU/L
Symptoms of hypothyroidism
Positive TPO antibodies
(+) evidence of heart disease
Treatment si clinical hypothyroidism and goal
Low dose L thyroxine 25-50
Goal: normalize TSH
Idiosyncratic side effect of levothyroxine replacement in children
Pseudo tumor cerebri
TSH goals in pregnant women
Mortality rate of myxedema coma
20-40%
Clinical manifestations of myxedema coma
Reduced level of consciousness
Seizures
Hypothermia
Precipitated by: Drugs Pneumonia CHF MI GI bleeding CV events
Plays a major role in the pathoenesis of myxedema coma
HYPOVENTILATION,
Leading to hypoxia and hypercapnia