Thyroid Gland

Right lobe

1

Isthmus

2

Left Lobe

3

Middle thyroid vein

1

Inferior thyroid vein

2

Superior thyroid arthery and vein

3

Inferior thyroid artery

4

Follicular cells

Synthesize and secrete thyroid hormones

blood, follicular, acetylcholine, thyroid

Histology → Follicular Cells

• Autonomic Nervous System neurons terminate in ______ vessels of thyroid and on ____________ cells

• Signals from ____________, catecholamines, and other peptides travel through this and will prompt follicular cells to secrete ________ hormone

Colloid

Stores thyroid hormone

iodine, thyroid, calcitonin, ghrelin

Histology

• Colloid

  • Concentrates ________ that is imported through blood supply, which is necessary for process of producing ________ hormone

• Parafollicular cells (AKA C cells)

  • Secrete regulatory peptides → __________, small amounts of neuropeptides ________, serotonin, and somatostatin

iodine, thyroglobulin, T3, T4, storage

Thyroid Hormone Synthesis

• It uses ________ (from food) and a protein called ______________ to make two main hormones

  • __ (triiodothyronine) - active form

  • __ (thyroxine) - _________ form that becomes T3 in the body

iodide, sodium, activated, thyroid peroxidase, thyroglobulin, follicular, tyrosine

Thyroid Hormone Synthesis

• _________ enters the thyroid

  • From your died (iodized salt, seafood)

  • Transported into the thyroid cells by a special “pump” called the __________-iodide symporter (NIS)

• Iodine is _________

  • Iodide is converted into a reactive form (iodine) by the enzyme ______ __________ (TPO) (Job #1)

• ___________ is made

  • This is a large protein made by thyroid ___________ cells, rich in __________ (an amino acid)

tyrosine, TPO, MIT, DIT, TPO, T3, T4

Thyroid Hormone Synthesis

• Iodine + ___________ = MIT and DIT

  • Iodine is added to tyrosine residues on thyroglobulin (facilitated by ___ → Job 2)

    • One iodine = ___

    • Two iodine = ___

• Coupling Reaction

  • Facilitated by ___ (job 3)

  • MIT + DIT = __ (active form)

  • DIT + DIT = __ (storage form)

thyroglobulin, colloid, blood, TSH, pituitary

Thyroid Hormone Synthesis

• Storage in colloid

  • These T3 and T4 hormones stay attached to _____________ in a gel-like substance called the ________, inside thyroid follicles

• Release into the ______

  • When the body needs thyroid hormone (signaled by ___ from teh __________ gland)

    • The thyroid takes in the thyroglobulin

    • T3 and T4 are cut free and released into the bloodstream

active, directly, 1, 1, beta, storage, T3, liver

Thyroid Hormones

• Triiodothyronine (T3)

  • 10% produced from thyroid gland

  • _______ form

  • __________ acts on target cells

  • Binds to thyroid receptors alpha-_, beta-_, _____-2

• Thyroxine (T4)

  • 90% of what thyroid gland produces

  • ________ form

  • Converted to __ within body tissues, mostly ______

• These bound forms serve as thyroid hormone storage within circulation, active form of hormone is when unbound

Thyroxine-binding globulin, albumin, lipoproteins

What are the three carrier proteins that are used to primarily transport thyroid hormones?

large, unbound, nuclear, unbound, free, increased, decreased

Unbound Thyroid Hormone

• AKA Free Hormone

• Able to enter into cells, bound hormone is too ______ to cross cell membrane

• Only _________ T3 and T4 can enter the cells and bind to _________ receptors

• Labs

  • ________ = ____ hormone, free hormones are what is measured when checking true thyroid function (more accurate than total thyroid hormone)

• Impact on feedback system

  • Hypothalamus and pituitary monitor free T3 and T4, not total hormone levels

    • Low free T3/T4 → increased TRH by hypothalamus and increased TSH by pituitary → __________ thyroid hormone production

    • High free T3/T4 → decreased TRH by hypothalamus and decreased TSH by pituitary → __________ thyroid hormone production

T4, T3, liver, feedback

Deiodinase Enzymes

• Special enzymes to remove one iodine atom from __ → active form, __

• Occurs mostly in ______, but in various body tissues when stimulated by ________ system

catabolism, all, temperature, growth, CNS, cardiac, RBC, insulin

Thyroid Hormone Effects

• Metabolism → protein, fat, carb ____________

• Metabolic rate of ___ cells

• Body _____________

• _______ hormone secretion → skeletal health

• Muscle tone

• ___ development

• __________ rate, how body uses oxygen

• GI regulation

• ___ production

• Cholesterol turnover

• _________ antagonist