1.Secretion of thyroxin.
2.Secretion of calcitonin.
SURGICAL ANATOMY.
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? Weight---------20----25gm.? Right and left lobe connected by isthmus.
? SITUATION= C5 to T1 vertebra.
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? ISTHMUS = 2nd to 4th tracheal ring.THYROID HORMONE.
? 1. THYROXINE (T4 ).
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? 2.TRIIODOTHYRONINE (T3 ).? 3.TSH.
? 4.Free T3.
? 5.Free T4.
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HISTOLOGY? FOLLICULAR CELLS------
? Lining the follicles
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and secretes T3 and T4.? Active phase---columnar
? Resting phase ---cuboidal.
? Follicles contains COLLOID.
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? Parafollicular cells= secrete
CALCITONIN.
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? Promote hypocalcaemia and calcium
deposition in bone.
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? opposite to PTH.Hormone synthesis.
HORMONE BIOSYNTHESIS.
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IODINE TRAPING
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FORMATION OF T3 and T4.ORGANIFICATION
COUPLING REACTION.
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? Binding of iodine with TGB.
? MAJOR PRODUCT =
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? To form monoiodotyrosine? THYROXINE
and diodotyrosine.
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? 2 Molecules of
diiodotyrosine
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? DIT + DIT = THYROXINE(T4).? MIT + DIT = T3.
RELEASE OF T3 and T4.
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T3 and T4 DIFFUSES OUT OF THYROIDCELL INTO SURROUNDING
CAPILLARIES.
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PHYSIOLOGICAL ACTION.
REGULATION.
? Synthesis and liberation of thyroid hormone is
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controlled by TSH = From anterior Pituitary.
? Secretion of TSH depend on level of T3 and T4.
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= NEGATIVE FEEDBACK MECH........? Regulation of TSH ----- By TRH From
HYPOTHALAMUS.
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HYPERTHYROIDISM.
? A form of thyrotoxicosis due to inappropriately
High synthesis and secretion of thyroid hormones
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by thyroid.
? Grave's disease is the most common cause, it is
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due to IgG auto-antibodies to TSH called LATS-long acting thyroid stimulator. They bind to TSH
receptor and continuously stimulate it leading to
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increased T3 and T4 secretion.
? Toxic nodular goitre usually due to adenoma or
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cancer of the thyroid.COMMON SYMPTOMS.
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? Excessive sweating? Weight loss
? Heat intolerance
? Increased bowel movement
? Tremor
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? Nervousness/agitation? Rapid heart rate/palpitation.
? Insomnia
? Breathlessness
? Irregular or scant menstrual periods
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Common signs? Hyperactvity/hyperkinesis
? Sinus tachycardia
? Systolic hypertension
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? Warm, moist, soft and smooth skin, warmhand.
? Excessive perspiration
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? Lid lag and stare(sympathetic overactivity)? Fine tremor
Lab. Finding in hyperthyroidism.
DIAGNOSIS.
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? 1.Typical clinical presentation? 2.markedly suppressed TSH( < 0.05)
? 3.Elevated FT4 and FT3.
? 4.Thyroid antibodies
? 5.ECG to demonstrate cardiac manisfestation
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? Nuclear scintigraphy to differentiate the cause.role of imaging in hyperthyroidism.
? Thyroid ultrasound
? Colour doppler helpful.
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? May reveal nodular disease or increased vascularity( seen in Grave's )
? Thyroid uptake and scan
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? High uptake? Grave's, toxic MNG, Toxic adenoma
? Low uptake
? Thyroditis, iodine induced hyperthyroidism.
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