Anterior to cricoid cartilage
Location of thyroid gland
Two symmetrical lobes fused by
blood supply by
sup and inf thyroid artery....forms a plexus
2 precursors of thyroid hormone
1. Iodide 2. Thyroglobulin
Very high doses of Iodide will
rapidly shut down thyroid hormone production in hyperhroid patients
Thyroid perixidase TPO
oxidizes iodide to iodine...
What inhibits TPO?
Carbimazole (among other drugs)....so you can't oxidize I2 into I-...ultimately cant make thyroid hormone
DIT + DIT =
MIT + DIT =
Endocytoses the TG-T3/4 complex from the colloid into the follicular cell.
Each step is under TSH control
Sodium iodide symporter
Diagnostic thyroid gland tests
Antibodies stimulate TSH receptor
Tachycardia, opthalmopathy, irritability, hyperactivity, heat intolerance, weight loss, nervousness, muscle wasting.
I- cannot be added to thyroglobulin in colloid.
Predominant in liver
Type I de-iodinase
Inner ring deiodinase (makes reverse T3)
mainly in brain and pituitary (this is the T3 being sensed by pit thyrotropes that is the negative feedback signal)....also in placenta
Which has highest affinity for T4?
Upon TSH stimulation, follicular cells (surrounding colloid) turn from
squamous to cuboidal
Inactivated follicles have flattened _____ epithelium
Parafollicular cells (C-cells) secrete
5 cell types thyroid gland
Epithelial Fibroblasts Lymphocytes Adipocytes C-cells
Parafollicular cells dont touch
2 precursors for TH
Less than 20micrograms per day of Iodine