3 - Thyroid Flashcards
What’s the difference between T3 and T4?
T3 has three iodine atoms and is much more potent
T4 has four
Levothyroxine is T___
T4
Thyroid hormones have three principal actions:
- Stimulation of energy use
- stimulation of the heart
- promotion of growth and development
What is the purpose of T4 and T3?
T3 exerts practically all of the effects of thyroid hormone
T4 only serves as a source of T3 in the tissues
How does T3 exert its effects?
Penetrates the nuclear membrane and binds with nuclear receptors, which in turn bind to specific DNA sequences
Results in increased production of the proteins associated with thyroid activation
Why does iodine deficiency cause goiters?
The drop in thyroid hormone production promotes release of TSH, which hypertrophies the thyroid in an attempt to increase secretion
What is the most sensitive method of detecting hypothyroidism?
TSH levels
The anterior pituitary is EXQUISITELY sensitive to changes in thyroid levels
In primary hypothyroidism, TSH should be ______
In secondary hypothyroidism, TSH should be ______
Primary (thyroid problem): High
Secondary (AP problem): Low
What is myxedema?
A severe level of hypothyroidism
SKIN
HYPO AND HYPER
Hypo: Cold and Dry, har is brittle with hair loss
Hyper: Warm and Moist, with heat intolerance
CARDIAC
HYPER AND HYPO
Hypo: Bradycardia, Hypotension
Hyper: Tachycardia, Hypertension
In countries where iodine deficiency is rare, what is the primary cause of hypothyroidism?
Hashimoto Thyroiditis - an autoimmune disease
What are the primary deficits a neonate of a mother with hypothyroidism will most likely develop?
Thyroid hormones are primarily responsible for neurological and skeletal mm development
Children will have neuropsychological issues and stunted growth
When women taking thyroid supplements get pregnant, what should happen to their synthroid dose?
It should be increased, often by as much as 50%
When are the effects of maternal hypothyroidism on the fetus the highest?
During the first trimester
Once the baby’s thyroid is developed, it can make its own thyroid hormone
With untreated congenital hypothyroidism, how will a child appear?
Large and protruding tongue
potbelly
dwarfish stature
In children who have hypothyroidism, how long do they require treatment?
After three years, we stop replacement therapy for four weeks and see what happens
If thyroid levels drop, it’s permanent and they’ll require lifelong treatment
There are two major forms of hyperthyroidism:
Grave’s Disease
Plummer Disease
What is plummer disease?
toxic nodular goiter (much less common than Grave’s disease)
It’s caused by a thyroid adenoma
What are some physical characteristics that can help determine whether hyperthyroidism is caused by Plummer disease or Graves Disease?
Exophthalmos that’s seen in Grave’s disease is due to an immune reaction, not to thyroid hormone levels
A patient with Plummer disease will not have exophthalmos
What symptoms are associated with Graves Disease?
Thyrotoxicosis
Exophthalmos
What are the symptoms of thyrotoxicosis?
Increased appetite with weight loss (increased BMR)
nervousness, insomnia, rapid thoughts, rapid speech
Skeletal mm may weaken and atrophy
Thyroid stimulation in Graves Disease is caused by:
Thyroid Stimulating Immunoglobulins (TSIs), which mimic the effects of TSH
by stimulating receptors for TSH on the thyroid gland
What is the preferred treatment for adult hyperthyroidism?
Pediatric hyperthyroidism?
Adult: Radiation
Pediatric: Antithyroid drugs
