Disorders of Thyroid - PowerPoint PPT Presentation

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Disorders of Thyroid

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Title: Disorders of Thyroid


1
Disorders of thyroid parathyroid glands
  • M.Prasad Naidu
  • MSc Medical Biochemistry,
  • Ph.D.Research Scholar

2
Disorders of thyroid parathyroid glands
  • 1. Hyperthyroidism
  • 2. Thyroid Adenoma
  • 3. Graves disease

3
Hyperthyroidism
  • Causes
  • Due to the presence of TSH like substances
    proved by RIA studies
  • The conc of TSH was found to be 0/less in plasma
    of Hyperthyroidism patients
  • The TSH like substances are Abs which bind with
    same membrane receptors of TSH
  • These substances activate c-AMP system ?T4
  • These Abs act for long time (12hrs) (TSH-1hr)
  • The ? of high T4 caused by Abs suppresses TSH
    production
  • Usually these Abs are developed b/cos autoimmunity

4
Thyroid Adenoma
  • Some times localised tumor develops in Thyroid
    tissue called Thyroidadenoma
  • TA secretes large quantities of T4T3
  • It is not associated with autoimmunity
  • As far as this adenoma remains active, the other
    parts of Thyroid gland will not secrete the
    hormone.
  • This is b/cos the hormone from Adenoma ?
    depresses the production of TSH

5
Graves disease
  • Autoimmune disease
  • Normally TSH combines with surface receptors of
    thyroid cells ? syn of T4
  • But in GD , the TSH autoAbs (B-TSAB) produced by
    B-lymphocytes (Plasma cells) activate the
    TSH-receptors ? secretion of T4

6
Symptoms of Hyperthyroidism
  • Intolerance to heat ( due to ? BMR)
  • ? sweating ( due to vasodialation)
  • ? body wt ( Fat metabolism)
  • ? motility of GIT ? diarrhoea
  • Muscular weakness ? ?protein catabolism
  • Nervousness, extreme fatigue, inability to sleep,
    mild tremor in the hands, psychoneurotic symptoms
    such as extreme anxiety/worry (stimulation of
    CNS)
  • Enlargement of Thyroid gland? i.e, Toxic goiter
  • Exophthalmos Autoimmune
  • some degree of protrusion of eye balls if
    severe blindness develops due to
  • i)protrusion of eye ball stretches the optic
    nerve
  • Ii) eye lids cannot be closed ? dry ? infection

7
hypothyroidism
  • ? secretion of Thyroid hormones
  • Autoimmune disease which causes destruction of
    Gland
  • In most patients it starts as the glandular
    inflammation called Thyroiditis
  • Thyroiditis ? fibrosis of the gland
  • Hypothyroiditis? Myxedema (adults) Cretinism
    (Children)

8
Myxedema
  • Due to hypothyroidism in adults
  • Causes occurs in severe conditions complete
    lack of thyroid hormones
  • Signs symptoms
  • Swelling of the face
  • Bagginess under the eyes
  • Non-pitting type of edema- when pressed it does
    not make pits and the edema is hard (accumulation
    of Procho.SO4 which form hard tissue with ?
    accumulation of fluid)
  • Atherosclerosis ? cholesterol blood ? bp

9
Myxedema
  • Other general symptoms
  • Fatigue muscular sluggishness
  • Extreme somnolence ( 14-16 hrs/day)
  • Menorrhagia polymenorrhea
  • ? Cordiovascular functions such as ?heart rate, ?
    force of contraction of heart ? crodiac out put ,
    ? blood volume
  • ?Body wt
  • Constipation
  • Mental sluggishness
  • ? hair growth
  • Scaliness of the skin
  • Frog like husky voice

10
Cretinism
  • Children
  • Causes congenital absence of thyroid gland
    (genetic disorder or lack of I2 in diet)
  • Features
  • The newborn baby may appear normal at birth (due
    to supply of T4 from mother)
  • But after few weeks starts developing sluggish
    movements croacking sound while crying ? mentally
    retarded
  • Skeletal growth is more affected than soft
    tissues
  • Tongue becomes so big affects swallowing
    breathing
  • Stunted growth

11
Differences b/n Cretinism Dwarfism
CRETINISM DWARFISM
Mental retardation Development of Nervous system is normal
Diff parts of the body are disaapropriate Proportionate
Reproduction system is affected normal
12
Goiter
  • Enlargement of thyroid gland
  • Occurs both in hypothyroidism Hyperthyroidism
  • Goiter in Hyperthyroidism ? Toxic Goiter
  • Due to tumor of the gland Size ? - ? number of
    hormones secreting cells ? hormone level
    Toxic Goiter
  • Goiter in hypothyroidism non toxic Goiter
  • Only enlargement of gland hormone secretion is ?

13
Goiter
  • Based on the cause, Non-toxic Goiter is of 2
    types
  • i) Endemic Colloid Goiter-
  • Due to lack of I2 I2 intake lt50µg/day
  • Therefore no formation of hormones
  • By feed back mechanism, hypothalamus and anterior
    pituitary are stimulated
  • This ? secretion of TRH and TSH ? secretion of
    TGb? Follicles
  • As there are no hormones to be cleaved, ?
    accumulation in the follicles
  • Therefore ? size of the gland
  • In Swiss, Alps, Andes, Great region of US and in
    India Kashmir Valley? Soil does not I2?
  • Therefore Food stuffs lack I2 very common
    before the introduction of iodized salts

14
Idiopathic Non-toxic Goiter
  • Enlargement of Thyroid gland occurs even without
    I2 deficiency
  • Exact cause not known
  • These patients are first affected by Thyroiditis
    which reduce synthesis of Thyroid hormones
  • Therefore secretion of TSH ?
  • ? Size of the gland
  • In some persons the abnormal enzyme system leads
    to Goiter(due to deficiency of enzymes like
    peroxidase, iodinase and deiodinase which are
    required synthesis of T3T4)

15
Idiopathic Non-toxic Goiter
  • Goitrogenic Substances ( Goitrogens)
  • Eg Goitrin
  • Contains antithyroid substances like
    propylthiouracil
  • Therefore TSH secretion ? enlargement of Thyroid
    gland
  • Goitrogens ? in turnips, cabbage, soyabeans
  • The goitrogens become active only during low I2
    intake

16
Treatment for Thyroid disorders
  • Treatment for Hyperthyroidism-
  • 1. Surgical removal Thyroidectomy
  • 2. Antithyroid substances Thiocyanate,
    thiourylenes, high conc of inorganic iodides
  • Treatment of hypothyroidism
  • Only treatment is administration of Thyroid
    extract/ ingestion of pure thyroxine ( tablet)

17
Anti thyroid substances
  • Drugs which supress the secretion of T3T4
  • 1. Thiocyanate the same active pump which
    transports I- into Thyroid cells, transports
    thiocyanate also
  • So thiocyanate competitively inhibits I2
    transport
  • I2 transport is inhibited
  • ? synthesis of Thyroxine

18
Thiourylenes
  • Thiourea related substances
  • Eg Propylthiouracil and methimazole prevent the
    formation of T4 from iodides and Tyr
  • This is achieved by blocking peroxidase activity
    and partly by blocking coupling of MIT DIT
  • During the use of these two antithyroid agents
    even though the synthesis of Thyroid hormone is
    inhibited , the formation of TGb is not stopped
  • The deficiency of the hor ? TSH secretion ? Size
    Thyroid gland with more secretion of TGb
  • TGb accumation in gland ? enlargement ? non-toxic
    G

19
High conc of inorganic iodides
  • All phases of Thy.activity ?
  • ? release of Thyroxine
  • ? Size
  • ? blood supply
  • Therefore iodides are frequently administrated
    to hyperthyroid patients

20
Thyroid function Tests
  • The most accurate diagnostic test is? Direct
    measurement of conc of Free thyroid hormones in
    the plasma (T3T4)
  • Measurement of BMR-
  • In Hyperthyroidism, ? 30-60
  • In hypothyroidism, ? 20-40
  • The measurement of TRH and TSH-
  • In Hyperthyroidism? total absence of TRH TSH
    (due to ve feed back mechanism by the ?level of
    Thyroid hormones)
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