Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Latest Thyroid Lecture PPT
THYROID.
? LARGEST GLAND IN THE BODY.
? FUNCTION =
1.Secretion of thyroxin.
2.Secretion of calcitonin.
SURGICAL ANATOMY.
? Weight---------20----25gm.
? Right and left lobe connected by isthmus.
? SITUATION= C5 to T1 vertebra.
? ISTHMUS = 2nd to 4th tracheal ring.
THYROID HORMONE.
? 1. THYROXINE (T4 ).
? 2.TRIIODOTHYRONINE (T3 ).
? 3.TSH.
? 4.Free T3.
? 5.Free T4.
HISTOLOGY
? FOLLICULAR CELLS------
? Lining the follicles
and secretes T3 and T4.
? Active phase---columnar
? Resting phase ---cuboidal.
? Follicles contains COLLOID.
? Parafollicular cells= secrete
CALCITONIN.
? Promote hypocalcaemia and calcium
deposition in bone.
? opposite to PTH.
Hormone synthesis.
HORMONE BIOSYNTHESIS.
IODINE TRAPING
FORMATION OF T3 and T4.
ORGANIFICATION
COUPLING REACTION.
? Binding of iodine with TGB.
? MAJOR PRODUCT =
? To form monoiodotyrosine
? THYROXINE
and diodotyrosine.
? 2 Molecules of
diiodotyrosine
? DIT + DIT = THYROXINE(T4).
? MIT + DIT = T3.
RELEASE OF T3 and T4.
T3 and T4 DIFFUSES OUT OF THYROID
CELL INTO SURROUNDING
CAPILLARIES.
PHYSIOLOGICAL ACTION.
REGULATION.
? Synthesis and liberation of thyroid hormone is
controlled by TSH = From anterior Pituitary.
? Secretion of TSH depend on level of T3 and T4.
= NEGATIVE FEEDBACK MECH........
? Regulation of TSH ----- By TRH From
HYPOTHALAMUS.
HYPERTHYROIDISM.
? A form of thyrotoxicosis due to inappropriately
High synthesis and secretion of thyroid hormones
by thyroid.
? Grave's disease is the most common cause, it is
due to IgG auto-antibodies to TSH called LATS-
long acting thyroid stimulator. They bind to TSH
receptor and continuously stimulate it leading to
increased T3 and T4 secretion.
? Toxic nodular goitre usually due to adenoma or
cancer of the thyroid.
COMMON SYMPTOMS.
? Excessive sweating
? Weight loss
? Heat intolerance
? Increased bowel movement
? Tremor
? Nervousness/agitation
? Rapid heart rate/palpitation.
? Insomnia
? Breathlessness
? Irregular or scant menstrual periods
Common signs
? Hyperactvity/hyperkinesis
? Sinus tachycardia
? Systolic hypertension
? Warm, moist, soft and smooth skin, warm
hand.
? Excessive perspiration
? Lid lag and stare(sympathetic overactivity)
? Fine tremor
Lab. Finding in hyperthyroidism.
DIAGNOSIS.
? 1.Typical clinical presentation
? 2.markedly suppressed TSH( < 0.05)
? 3.Elevated FT4 and FT3.
? 4.Thyroid antibodies
? 5.ECG to demonstrate cardiac manisfestation
? Nuclear scintigraphy to differentiate the cause.
role of imaging in hyperthyroidism.
? Thyroid ultrasound
? Colour doppler helpful.
? May reveal nodular disease or increased vascularity
( seen in Grave's )
? Thyroid uptake and scan
? High uptake
? Grave's, toxic MNG, Toxic adenoma
? Low uptake
? Thyroditis, iodine induced hyperthyroidism.
This post was last modified on 30 November 2021