Thyroid Hormones: T3 and T4 Functions and Mechanisms

T3

Triiodothyronine, more active thyroid hormone.

T4

Thyroxine, less active thyroid hormone.

Thyroid hormone-binding globulin

Main protein that binds thyroid hormones in blood.

Transthyretin

Transport protein for thyroid hormones in circulation.

Albumin

Common blood protein that carries thyroid hormones.

Monodeiodination

Conversion of T4 to T3 in target cells.

Deiodinase enzymes

Enzymes that regulate thyroid hormone activity.

Iodothyronine deiodinases

Types I, II, III enzymes (D1, D2, D3) for T4 conversion.

D1

Deiodinase type I, converts T4 to T3.

D2

Deiodinase type II, activates T4 to T3.

D3- which type and inactive what to reverse

Deiodinase type III, inactivates T4 to reverse T3.

Nuclear receptors

Thyroid hormone receptors that regulate gene expression.

Hydrophobic nature

Thyroid hormones require transport proteins for cell entry.

Gene expression modulation

Thyroid hormones influence transcription factors in cells.

Placental thyroid hormone levels

High levels of thyroid hormones during pregnancy.

What is the role of ATP in sodium reabsorption?

Answer: It is used to power the

Explanation: ATP provides the energy necessary for the ………. to actively transport ……. out of the which cells and into the which fluid, crucial for creating the what for water ……….

Answer: It is used to power the Na⁺/K⁺ ATPase pump

Explanation: ATP provides the energy necessary for the Na⁺/K⁺ ATPase pump to actively transport sodium out of the epithelial cells and into the interstitial fluid, crucial for creating the osmotic gradient for water reabsorption.