Thyroid Lecture

THYROID PHYSIOLOGY
Presentation lecture by:Jack L. Leonard, Ph.D.
umassmed.edu

THE THYROID GLAND
THYROID GLAND HISTOLOGY
THYROID FOLLICULAR
CELL MORPHOLOGY
THYROID HORMONES
FEEDBACK REGULATION
THE HYPOTHALAMIC-PITUITARY-THYROID AXIS
Hormones derived from the pituitary that regulate the synthesis and/or secretion of other hormones are known as trophic hormones.

Key players for the thyroid include:

TRH - Thyrophin Releasing Hormone
TSH - Thyroid Stimulating Hormone
T4/T3 - Thyroid hormones

PITUITARY-THYROID AXIS
PITUITARY-THYROTROPE CELL

* TSH binds to specific cell surface receptors that stimulate adenylate cyclase to produce cAMP.
* TSH increases metabolic activity that is required to synthesize Thyroglobulin (Tg) and generate peroxide.
* TSH stimulates both I- uptake and iodination of tyrosine resides on Tg.

TSH REGULATION OF THYROID FUNCTION
ION TRANSPORT BY THE THYROID FOLLICULAR CELL
THYROID HORMONE SECRETION BY THE THYROID FOLLICULAR CELL
THYROID HORMONES IN THE BLOOD
THYROID HORMONE METABOLISM
THYROID HORMONE DEIODINASES

* Three deiodinases (D1, D2 & D3) catalyze the generation and/disposal of bioactive thyroid hormone.
* D1 & D2 “bioactivate” thyroid hormone by removing a single “outer-ring” iodine atom.
* D3 “inactivates” thyroid hormone by removing a single “inner-ring”iodine atom.
* All family members contain the novel amino acid selenocysteine (SeC) in their catalytic center.

BASIC ORGANIZATION OF THE SELENODEIODINASES
BASICS OF THYROID HORMONE ACTION IN THE CELL
STEROID/THYROID HORMONE FAMILY OF NUCLEAR RECEPTORS
SPECIFIC ACTIONS OF THYROID HORMONE: METABOLIC

* Regulates of Basal Metabolic Rate (BMR).
* Increases oxygen consumption in most target tissues.
* Permissive actions: TH increases sensitivity of target tissues to catecholamines, thereby elevating lipolysis, glycogenolysis, and gluconeogenesis.
* TH is critical for normal development of the skeletal system and musculature.
* TH is also essential for normal brain development and regulates synaptogenesis, neuronal integration, myelination and cell migration.
* Cretinism is the term for the constellation of defects resulting from untreated neonatal hypothyroidism.

SPECIFIC ACTIONS OF THYROID HORMONE: DEVELOPMENT
EXAMPLES OF THYROID DISEASES
www.hsc.missouri.edu/~daveg/thyroid/thy_dis.html

Congenital Hypothyroidism
Juvenile Hypothyroidism

THYROID Lecture.ppt