(23) The Thyroid Gland (C) Flashcards
The thyroid gland is responsible for the production of two hormones:
thyroid hormone and calcitonin.
The parathyroid glands regulate:
serum calcium levels.
Congenital Hypothyroidism can lead to what conditions in newborns?
Mental retardation & cretinism (impaired physical or mental development).
Thyroid hormone is made primarily of what trace element?
Iodine.
What are the two active forms of thyroid hormone?
Triiodothyronine (T3) & Thyroxine (T4)
What thyroid hormone is the most metabolically active?
T3 (3 - 8X more active)
What are the three major binding proteins for thyroid hormones?
(1) Thyroxine-binding Globulin
(2) Thyroxine-binding Prealbumin
(3) Albumin
The most useful test for assessing thyroid function is:
Thyroid-Stimulating Hormone (TSH).
What is the benefit of TSH chemiluminometric assays over other methods?
(1) Increased sensitivity
(2) Fewer false-negatives
(3) Able to distinguish between euthyroidism and hyperthyroidism
What are the two common testing methodologies for T4 & T3?
(1) Radioimmunoassay (RIA)
(2) Chemiluminometric assay
Thyroglobulin is a protein synthesized and secreted by:
Thyroid follicular cells.
What test is an ideal tumor marker thyroid cancer posttreatment surveillance?
Thyroglobulin
Thyroglobulin is measured by what testing methodology?
(1) Double-antibody RIA
(2) Enzyme-linked immunoassay (ELISA)
(3) Immunoradiometric assay (IRMA)
(4) Immunochemiluminescent assay (ICMA)
What substance can interfere with thyroglobulin testing?
Antithyroglobulin autoantibodies.
What is the most common cause of hyperthyroidism?
Graves’ disease (autoimmune disorder).
Describe how Graves’ disease causes hyperthyroidism.
Antibodies are directed at TSH receptors, stimulating the receptor and causing an overproduction of thyroid hormone.
Describe how Hashimoto’s Thyroiditis causes hypothyroidism.
Antibodies lead to decreased thyroid hormone production by destruction of the thyroid gland (most common cause of hypothyroidism).
What is the best test to test for Hashimoto’s Thyroiditis?
TPO antibody.
Define radioactive iodine uptake (RAIU).
The percentage of iodine that is taken up by the thyroid gland after oral radioactive iodine is given.
How is FT4 and TSH affected by hypothyroidism.
Low FT4; normal or high TSH.
What are the physical signs of hypothyroidism?
Bradycardia & diastolic hypertension.
What are the symptoms of hypothyroidism?
Cold intolerance, depression, mental retardation.
The most common cause for hypothyroidism is:
Lymphocytic thyroiditis, or Hashimoto’s thyroiditis.
Hashimoto’s thyroiditis is an ________ disease targeting the ________.
autoimmune; thyroid gland.
Hashimoto’s thyroiditis is often associated with what physical symptoms?
Enlarged gland, or goiter.
What test is often positive when patients present with chronic lymphocytic thyroiditis?
TPO antibody.
Transient hypothyroidism is associated with:
inflammation of the thyroid gland.
Primary hypothyroidism is from a dysfunction of:
the thyroid gland.
Secondary hypothyroidism is from a dysfunction of:
pituitary.
Tertiary hypothyroidism is from a dysfunction of:
hypothalamic.
How is hypothyroidism treated?
Thyroid replacement therapy (Levothyroxine [T4]).
Define Thyrotoxicosis.
When peripheral tissues are presented with an excess of thyroid hormone.
What is the most common cause of thyrotoxicosis?
Graves’ disease.
Graves’ disease is a disease in which:
antibodies are produced that activate TSHR.
What laboratory testing would indicate Graves’ disease (hyperthyroidism)?
High FT4; High FT3; Low/Undetectable TSH.
Describe the Wolff-Chaikoff effect.
When iodine is given in large doses, this acutely leads to inhibition of thyroid hormone production.
Postpartum thyroiditis is strongly associated with the presence of:
TPO antibodies and chronic lymphocytic thyroiditis.
Painful thyroiditis is characterized by what symptoms?
Neck pain, low-grade fever, and swings in thyroid function testing.
Describe nonthyroidal illness or euthyroid sick syndrome.
Hospitalized/critically ill patients that have abnormalities on thyroid function testing without thyroid dysfunction.
What is the laboratory pattern for nonthyroidal illness or euthyroid sick syndrome.
Normal/low TSH; low T3; low FT4.
