IM
GENERAL POINTS ABOUT THYROID GLAND
- Normal sized thyroid is usually not palpable
- Moves up on swallowing
THINGS PRODUCED BY THYROID
- Thyroxine (T4) - hormones from follicles
- Tri-iodo-thyronine (T3) - hormones from follicles
- Calcitonin (produced by parafollicular cells)
- Thyroid peroxidase (TPO): an enzyme required in hormone synthesis
GENERAL POINTS ABOUT HORMONES
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“Balanced” amount of Iodine is needed for hormone synthesis ( so, its def. or even, excess can cause problems)
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Most of the T4 &T3 is bound to plasma proteins in the blood:
- a) Thyroxine binding globulin (TBG)
- b) Thyroxine binding pre-albumin
- c) Albumin
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The remaining free hormones are physiologically active( fT4 & fT3)
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Conditions which increase or decrease the plasma protein levels will affect the total hormone levels but free levels usually remain normal, so be careful while interpreting the results
CONTROL OF SECRETION
Hypothalamus produces TRH (thyrotropin releasing hormone) ⇒ stimulates the ant. pituitary ⇒ produces TSH (thyroid stimulating hormone) ⇒ stimulates thyroid gland ⇒ T4 & T3 produced
Thyroid Investigations
MAIN DISEASES OF THYROID
- Goiter
- Hyperthyroidism (overactive gland)
- Hypothyroidism (underactive gland)
- Thyroid adenomas, cysts, carcinoma