Changes in diurnal rhythm, stress, temperature, and metabolic state impact the activation of HPT axis
TRH Receptor on Anterior Pituitary Thyrotrope Cell
T4: Thyroxine
Liver (TRß1 Receptors)
Aids in the formation of LDL receptors
Regulates the basal metabolic rate of all cells, including hepatocytes; liver metabolizes the thyroid hormones and regulates their systemic endocrine effects
Auditory
Role in the mechanism of hearing
Skeletal Muscle (TRa1 Receptors)
Increases protein breakdown
Increases motor neuron stimulation by rapidly signaling for the activity for the sodium-potassium pump
All aspects of thyroid hormone synthesis and secretion occur as well as cell growth
Stimulates AC
TSH Receptor on Thyroid
TSH Synthesis and Secretion
Stimulates Ca2+ and PLC
TRH Neuron
T3: Triiodothyronine
Heart (TRa1 Receptors)
Chronotropic and ionotropic
Increases ß-adrenergic receptors
Decreased systemic vascular resistance (SVR) by a direct effect on the arteriolar smooth muscle cells
Bone
Increases growth of cartilage/bone turnover and aids in skeletal development
Brain (TRß1 Receptors)
Stimulates appetite
Regulates gene expression during fetal development
