THYROID GLAND

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• THYROID GLAND
• Ectopic thyroid MC at base of tongue (lingual
  thyroid)
• Histology lobules composed of about 20 to 40
  evenly dispersed follicles lined by Cuboidal to
  low columnar epithelium
• Physiology In periphery, free T4 ? T3
• T3 receptors on nuclear membranes of in target
  cells
• up-regulation of carbohydrate and lipid
  catabolism
• stimulation of protein synthesis
• ? BMR
• act on all cells in the body
• Thyroid, steroid vitamin D receptors are in the
  nucleus
• parafollicular cells, or C cells secrete the
  hormone calcitonin
• Both hypo and hyperthyroidism produce HTN
• Pharmacology Goitrogens ( mustard seeds and
  cabbage contain)
• suppress T3 and T4 synthesis, TSH
  increases-(Goiter)
• Propylthiouracil inhibits the oxidation of iodide
  ( inhibits thyroid peroxidase) ( indicated in
  pregnancy)
• Iodide blocks the release of thyroid hormones
• Best screening test for both hypo and hyper
  thyroid is TSH

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THYROID GLAND
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THYROID GLAND

• Pathology
• Hyperthyroidism
• Graves Disease
• Hypothyroidism
• Cretinism
• Myxedema
• Thyroiditis
• Hashimotos
• Subacute
• Granulomatous
• Lymphocytic (painless)
• Diffuse Multinodular Goiter
• Neoplasms

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• Hyperthyroidism
• Causes MCC - Graves disease (85 of cases)
• Others Toxic multinodular goiter ,Toxic
  adenoma, Struma ovarii
• Characterized by Hyper metabolic state
• clinical Nervousness, warm moist skin, fine
  tremors ( intention and resting), palpitations,
  rapid pulse ( sleeping pulse gt 100/min),
  exophthalmos, weight loss, heat intolerance,
  muscle atrophy weakness, osteoporosis
• lab ? circulating T3 ? T4, ?TSH
• Graves disease
• Peak age -20-40 yrs.
• ?incidence in females (F/M 101)
• Pathogenesis Autoimmune disorder of thyroid
  gland
• IgG antibodies against TSH receptors ( LATS)
• IgG act as agonists on receptors ? Increasing
  thyroid hormone secretion.
• Genetics Familial ( HLA-B8 HLA-DR3
  association)
• Clinically Symmetrical thyroid enlargement ,
  Hyperthyroidism, Opthalmopathy, Proptosis or
  exophthalmia , Dermopathy (pretibial myxedema)
• Lab ? T3 ? T4, ? TSH , ? radioactive iodine
  uptake I-131

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GRAVES DISEASE (HYPERTHRYRIODISM)
Scalloped appearance hyperfunctioning gland
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• Hypothyroidism
• Causes MCC in adults is Hashimotos Thyroiditis
• Others dietary iodine deficiency, Thyroid
  dysgenesis
• Characterized by Hypometabolic state
• Clinical
• Cretinism In children
• severe mental retardation, short stature, coarse
  facial features (protruding tongue due to?
  deposition of GAGs glycosaminoglycans )
• Myxedema in adults (GAGs deposition results in
  non-pitting edema, Coarsening of facial features,
  
• Clinical features
• Slowing of physical and mental activity Fatigue,
  lethargy, slowed speech, mental sluggishness,
  cold intolerance, weight gain , hyper
  cholesterolism
• ? in sympathetic activity Constipation, ?
  sweating, bradycardia

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• Hypothyroidism
• Hashimotos Thyroiditis
• Age- 45-65 yrs.
• FM 10 to 201
• MCC of hypothyroidism in USA
• Familial HLA-DR3 or HLA-DR5 Associated (weak)
• Clinically Seen predominately in middle-aged
  women as diffuse painless enlargement of the
  gland
• Pathogenesis Autoimmune disorder
• anti-thyroid antibodies ? AGAINST
• Thyroid peroxidase
• TSH-receptors ? blocking of thyroid hormone
  receptors
• Iodine transporter
• Thyroglobulin (TGB)
• Thyroid injury mediated by complement fixing
  Cytotoxic antibodies, ADCC CD8 Cytotoxic cells
• Associated conditions Turners and Downs
• Lab ?T3,?T4, ?TSH antibodies
• Risk of SLE, Sjogren's, DM (Type- I), NHL ( B
  cell)

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HASHIMOTOS THYROIDITIS Pathogenesis
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HASHIMOTOS THYROIDITIS Pathology

• Histology
• lymphoid aggregate tissue with reactive germinal
  centers
• Hurthle cell change eosinophilic cytoplasm)
• Destruction of follicles
• Fibrosis

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• Thyroiditis
• 1. Hashimotos
• 2. Sub acute Granulomatous or De Quervains
• Age 30-50 yrs.
• FM- 3-51
• Etiopathgenesis Viral or post viral (
  Coxsackie's, Mumps, Measles, Adeno)
• Pathology Early- Micro abscess, Neutrophils
• Late Granulomas with multinucleate giant cells
• Clinical course past history of URI
• Painful neck swelling
• Initial transient hyperthyroidism ( 2-6 weeks),?
  Transient hypothyroidism ? becomes Normal
• Lab ? T3, ? T4, ? TSH , ?I 131 uptake ( in
  Graves - ? T3, ? T4, ? TSH , ? I 131 uptake)
• 3. Sub acute Lymphatic ( painless) Thyroiditis
  Silent Thyroiditis
• Middle aged females with Hyperthyroidism (post
  partum Thyroiditis)
• Pathogenesis ? autoimmune

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• Thyroiditis contd .
• 3. Sub acute Lymphatic ( painless) Thyroiditis
  Silent Thyroiditis
• Morphology diffuse painless goiter
• Lymphocytic infiltrate with germinal centers (
  unlike Hashimotos no fibrosis or hurthle cell
  change)
• Lab ? T3, ? T4, ? TSH
• Clinical course Hyperthyroidism (unlike Graves
  without skin or ocular changes)
• Recurrent with subsequent pregnancies
• 4. Riedels Thyroiditis
• Unknown etiology
• Extreme fibrosis ( also retroperitoneal)
• Adherent to adjacent tissues
• DD Carcinoma of thyroid
• 5. palpation Thyroiditis
• Due to vigorous clinical palpation
• Chronic inflammation giant cells
• Lab No abnormalities

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• Diffuse Multinodular goiter
• Goiter enlargement of thyroid
• MC manifestation of thyroid disease
• MCC of Goiter dietary Iodine deficiency
• 1. Diffuse non toxic goiter ( Graves diffuse
  toxic)
• MCC regions of dietary Iodine deficiency
• Also called endemic goiter
• Morphology Follicles willed with colloid (
  colloid goiter)
• Lab normal T3 T4, ? TSH
• Clinical euthyroid,
• 2. Multinodular goiter develop from diffuse
  nontoxic goiters
• Clinically very large goiter ( 2000 mg wt.),
  painless,
• Produce pressure/ mass effects
• Nodularity uneven hyperplasia of follicles with
  hemorrhage, necrosis, scar
• Lab Euthyroid, varied I 131 uptake
• Plummer syndrome euthyroid becomes hyperthyroid
  ( with graves features)

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Multinodular goiter (adenomatous goiter)

• Secondary changes hemorrhage, fibrosis,
  calcification cystic degeneration

Calcification
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• Neoplasms of thyroid
• STN solitary thyroid nodule
• More common in female, advanced age,
• How to interpret STN?
• STN in young male neoplasm
• STN in a person with history of radiation
  malignancy
• Hot (increased I 131 uptake) hyperfunction, not
  neoplastic
• Cold decreased I 131 uptake) 10 malignant
• Lab Ultrasound or FNAC? Biopsy
• Benign neoplasm
• Adenoma Follicular adenoma
• Discrete, solitary,
• integrity or intact capsule ( extremely
  important) to differentiate from follicular
  carcinoma
• Carcinoma uncommon in USA
• More common in females, most are well
  differentiated

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Carcinomas of thyroid
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Carcinomas of thyroid
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1) PAPILLARY CARCINOMA
Nuclear inclusions
Pale nuclei orphan Annie eyes
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2) FOLLICULAR CARCINOMA
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3) MEDULLARY CARCINOMA

• MEN-associated (familial)
• Multicentric bilateral
• Peak 3rd-4th decades
• Amyloid deposits in the stroma (stroma look pink)
• Staining
• Positive for calcitonin,