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Thyroid Hormones

Terms in this set (26)

Thyroid follicular cells concentrate iodide (I-) via a __/ I- symporter
Na+
Iodide oxidized by the enzyme __________; the oxidation reaction creates reactive iodide intermediate that couples specific tyrosine residues on thyroglobulin
thyroid peroxidase
Thyroglobulin iodination is known as __________, which results in thyroglobulin molecules containing monoiodotyrosine (MIT) and diiodotyrosine (DIT) residues which have one or two covalently attached iodines respectively.
organification
MIT joined to DIT =
T3
DIT + DIT =
T4
____ (hypothalamus) -> _____ (pituitary) -> T3,T4 (thyroid gland)
TRH, TSH
In the absence of thyroid hormone, the thyroid hormone receptor (TR):retinoid X receptor (RXR) heterodimer (associates/dissociates) with a corepressor complex, which binds to promoter regions of DNA and inhibits gene expression.
associates
In the presence of thyroid hormone (T3), the corepressor complex (associates/dissociates) from the TR:RXR heterodimer, coactivators are recruited, and gene transcription occurs
dissociates
Congenital deficiency of thyroid hormone results in _______, a severe but preventable form of mental retardation.
cretinism
Excess TSH or TSH mimetics can cause enlargement of the thyroid (hypertrophied) known as
goiter
(autoimmune origin) causes HYPERthyroidism; IgG autoantibody specific for the TSH receptor AKA thyroid-stimulating immunoglobulin (TsIg) is produced and acts as an TSH AGONIST

-Activates the TSH receptor stimulating release of thyroid hormone; however TsIg is not subject to negative feedback control and continues to stimulate thyroid function even when plasma levels rise toward pathological levels
Graves disease
Clinical labs for a patient with graves disease would indicate _____ plasma thyroid hormone levels and ____ TSH levels and high TsIg levels
high, low
___________ results in HYPOthyroidism due to selective destruction of thyroid gland. Gradual inflammatory destruction.

-Antibodies specific for thyroid proteins (thyroid peroxidase, thyroglobulin)
Hashimoto's thyroiditis
___________, the L-isomer of T4 is treatment of choice for hypothyroidism
Levothyroxine
___ is used instead of T4 (Levothyroxine) in the case of myxedema coma, where the faster onset of ___ may provide enhanced recovery from life-threatening hypothyroidism
T3
isotope that strongly emits β-particles toxic to cells which selectively destroys the thyroid gland.
-Used to treat thyrotoxicosis, an alternative to surgery; however patients may eventually develop hypothyroidism 131I- is radioactive iodide
131I (radioactive iodide)
High levels of iodide inhibit thyroid synthesis and release, which is called the
Wolff-Chaikoff effect
This thioamine inhibits thyroid production by inhibiting thyroid peroxidase as well as peripheral T4 to T3 conversion
propylthiouracil (PTU)
This thioamine inhibits thyroid production by inhibiting solely thyroid peroxidase
methimazole
_________ is actively concentrated in the thyroid gland, high levels of _____ have been shown to inhibit thyroid release from thyroid follicular cells
lithium
Stimulates TSH release from pituitary gland. Used to diagnose thyroid function
Protirelin (TSH)
Stimulates thyroid gland to uptake iodide. Adjunctive treatment of malignant tumor of thyroid gland.
Thyrotropin (TSH)
Stimulates adrenal cortisol and androgen production. Used in diagnosis of adrenal cortical function.
Cosyntropin
Replaces missing endogenous thyroid hormones with exogenous thyroid hormones (name T3 and T4)
levothyroxine (T4) and Liothyronine (T3)
Iodide uptake inhibitor. compete for iodide for uptake into thyroid gland follicular cells via sodium-iodide symporter, thereby decreasing intra-thyroid supply of iodide available for thyroid hormone synthesis. (for hyperthyroidism)
perchlorate, thiocyanate
Drugs that increase the activity of P450 enzymes (Rifampin and phenytoin) _______ hepatic excretion of T4
increase
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