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Sodium Potassium Symport
◦Symports move particles in the same direction
◦Responsible for moving iodide to thyrocyte
Mitochondria proliferates in presence of hormone and mitochondrial hypertrophy (enlargement) occurs (individual mitochondrion become bigger)
Thyrotropin/Thyroid-Stimulating Hormone (TSH)
Hormone from pituitary gland that controls thyrocytes
How Does TSH Control Thyrocytes?
◦Hypertrophy = enlarges thyrocytes, allows it to make and secrete more T4
◦Hyperplasia = increase in number of cells, thyrocytes proliferate, mitogenic
Thyrotropin-Releasing Hormone (TRH)
Neurohormone from small gland attached to the base of the brain that regulates pituitary gland by stimulating it to secrete TSH
What Controls the Brain in the Secretion of TRH?
Secretion of T4 reduces number of TRH receptors on
pituitary gland (fewer receptors, lower pituitary response to TRH)
• Down-Regulation of receptors
◦Type of hyperthyroidism
◦Thyrocytes poisoned by abnormal antibodies (IgG) which compete with TSH for the same protein receptor and functions like TSH only more excessively
◦Increase in metabolic and heart rate (palpitations, arrhythmia), and oxygen consumption, exophthalmos, transplacental
◦High T4 levels will cause positive feedback on the brain, causing it to produce lower levels of TRH and therefore lower TSH
•Treatment 1: Radioactive iodine
•Treatment 2: Immunosuppression (Higher mortality rate)
•Treatment 3: Synthroid
•Treatment 4: Subtotal Thyroidectomy
•Treatment 5: Thiouracil
•Treatment 6: Thiocyanates
A membrane transport process that carries two substances in the same direction across the membrane.
Radioactive Iodine Treatment
"Hot" or radioactive iodine will compete with the "cold" or regular iodine and cell that intakes radioactive iodine will be destroyed by the radiation
◦Sodium iodide symports can get thyrocytes to take up
◦Iatogenic: patient will emit gamma radiation and will be unsafe for a while
Thyroid Stimulating Immunoglobin (IgG)
Abnormal antibody that competes with TSH for the same protein receptor and functions like TSH only more excessively, causing Graves Disease
Eyes bulge because of eyeball volume increase so that
eyeball cannot ﬁt in orbital cavity which will cause deteriorating vision
Condition of hyposecretion of the thyroid gland causing low thyroid levels in the blood that result in sluggishness, slow pulse, and often obesity
Condition of hypersecretion of the thyroid gland characterized by exophthalmia, tachycardia, goiter, and tumor
7x greater incidence than Graves disease
‣ Primary and Secondary Diagnosis
◦Symptoms: Puffy eyes, apparent obesity (redistribution of polysaccharide), lethargy and stupor, low consumption of oxygen, decrease in metabolic rate
‣ Hashimoto antibody destroys TSH receptors, causes atrophy in thyroid > Insufﬁcient T4 levels (brain is un-suppressed) elevation of both TRH and TSH
Treatment with T4 when thyroid destroyed
Used to treat Hashimoto's Thyroiditis
-Mostly found in inland populations
-Cause: dietary deficiency of iodine
‣ Adequate T4 cannot be made > brain un-suppressed by loss of T4 > elevated TRH > elevated TSH
• Still binds to TSH receptors and will cause hypertrophy and induce mitosis in thyrocytes
Relationship Between TRH, TSH and T4
TRH > +TSH > +T4
•T4 will then act in positive feedback to inhibit TRH and TSH
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