Lect 3-thyroid disorders

1. Thyroid Gland Disorders
SMS3023
By: Dr. Mohanad

2. Thyroid Gland: Introduction
The largest pure endocrine gland (15-25 gm), located in the anterior neck
Consists of two lateral lobes connected by a median tissue mass called the isthmus.
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3. Thyroid Gland: introduction
Blood supply
Arterial blood supply
Superior thyroid artery from external carotid
Inferior thyroid artery from subclavians
Blood flow 4-6 ml/min/gm
Venous blood supply
Three pairs of veins supply blood to the gland
4. Thyroid Gland: introduction
The thyroid gland is made up of closely packed sacs called thyroid follicles.
The structural and functional unite of thyroid gland.
Cyst-like structure
0.2 0.9 mm in diameter
Simple cuboidal epithelial (follicular cells) surrounding a lumen filled with colloid.
T4 andT3 present in colloid bound to a large protein called thyroglobulin.
5. Thyroid follicles
6. Thyroid follicles
7. Thyroid Follicles
Thyroid gland secret 3 hormones
Thyroxin or (T4)
Tri-iodotyronine or (T3)
Main hormones secreted by thyroid gland
Secreted by follicular cells
Amino acid derivatives (tyrosine)
Calcitonin
Produced by parafollicular cells C cells
9. Hypothalamus-Pituitary-Thyroid Axis
Synthesis of T4 and T3 are stimulated by:
TSH
Synthesis of T4 and T3 are reduced by:
TSH
Glucocorticoid, dopamin and somatostatine.
11. Actions of Thyroid Hormones
Increase the bodys overall basal metabolic rate
Increase oxygen consumption
Essential for normal growth
Mental development
Sexual maturation
Increase the sensitivity of CVS and CNS to catecholamines (COP and HR)
12. Diseases of the Thyroid Gland
Congenital diseases
Inflammation
Functional abnormality
Diffuse and Multinodular goiters
Neoplasia
13. Congenital Thyroid Diseases
Agenesis /Aplasia
Hypoplasia
Accessory or aberrant thyroid glands
Thyroglossal duct cyst
14. Thyroglossal Duct Cyst
A thyroglossal duct cyst is a neck mass or lump that develops from cells and tissues remaining after the formation of the thyroid gland during embryonic development.
Children
Failure of regression
Neck, medial
Squamous or columnar lining
often appears after an upper respiratory infection when it enlarges and becomes painful.
Complications: inflammation,
sinus tracts
15. Inflammation
Thyroiditis
Acute illness with pain
Infectious
Acute
Chronic
Subacute or granulomatous (De Quervains)
Little inflammation with dysfunction
Subacute lymphocytic thyroiditis
Fibrous (Riedel) thyroiditis
Autoimmune
Hashimoto thyroiditis
16. HASHIMOTO THYROIDITIS
Most common cause of hypothyroidism
Autoimmune, non-Mendelian inheritance
45-65 years, F:M = 10-20:1
Painless symmetrical enlargement
Risk of developing
B-cell non-Hodgkins lymphoma
Other concomitant autoimmune diseases
Endocrine and non-endocrine
17. Hashimoto ThyroiditisPathogenesis
Immune systems reacts against a variety of thyroid antigens
Progressive depletion of thyroid epithelial cells which aregradually replaced by mononuclear cells -> fibrosis
Immune mechanisms may includes:
CD8+ cytotoxic T cell-mediated cell death
Cytokine-mediated cell death
Binding of antithyroid antibodies -> antibody dependent cell-mediated cytotoxicity
18. Morphology-Hashimoto Thyroiditis
Diffuse enlargement
Firm or rubbery
Pale, yellow-tan, firm & somewhat nodular cut surface
firm consistency: may be confused with carcinoma
not stony hard as in Riedel's thyroiditis
a distinctly multinodularqualityfascial attachment to the tracheal wall slightly thickened, but no strong fixation
19. Morphology
Necrosis
Calcification
Resembles a hyperplastic lymph node
Resembles a hyperplastic lymph node
20. Histopathology-Hashimoto Thyroiditis
Massivelymphoplasmcyticinfiltration with lymphoid follicles formation
Destruction of thyroid follicles
Remaining follicles are small and many are lined by Hurthle cells
Increased interstitial connective tissue
plasma cells, histiocytes
scattered intrafollicular multinucleated giant cells
Polyclonal lymphoplasmacytic population
ashimoto's thyroiditis showing lymphoid follicles with prominent germinal centers and oncocytic follicular epithelium.
21. Histopathology-Hashimoto Thyroiditis
Follicles: small and atrophic
most lined by variably sized Hrthle cells
Nuclei of Hrthle cells may be: enlarged and hyperchromaticoptically clear and overlapping (reminiscent of papillary carcinoma)
Squamous nests: thought to arise from metaplasia of follicular cells
Hashimoto's thyroiditis with extensive fibrosis, atrophy of follicular epithelium, and squamous metaplasia.
22. Follicles: small and atrophic
23. Hashimoto's thyroiditis
This symmetrically small thyroid gland demonstrates atrophy.
This is the end result of Hashimoto's thyroiditis.
24. Hashimoto's thyroiditis
A lymphocytic infiltration with prominent follicles with germinal centers
25. Symptoms
Fatigue, Depression
Modest weight gain,Cold intolerance
Excessive sleepiness,Dry, coarse hair, Dry skin
Constipation, Increased cholesterol levels
Muscle cramps, Decreased concentration
Vague aches and pains,
Swelling of the legs
26. Thyroid disorders
Hypothyroidism
Underactive thyroid
Hyperthyroidism
Overactive thyroid
Goiter
Thyroid enlargement
27. Hypothyroidism
Outlines
Definition
Causes
Clinical features
Investigation
Treatment
28. Hypothyroidism
Definition
A clinical and biochemical syndrome that results from a deficiency in thyroid hormone secretion from thyroid gland or in the action
The disease ranges from subclinical hypothyroidism to primary and secondary hypothyroidism and the extreme medical emergency, myxoedema coma.
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Hypothyroidism
Prevalence
It is a common disorder with prevalence ranges from 2-15% population
>
Female to male ratio = 10:1
with age; =
Mean age at diagnosis is 50 years
30. Primary Hypothyroidism
Disease of the thyroid gland
Secondary Hypothyroidism
Hypothalamic-pituitary diseases (reduced TSH)
Hypothyroidism
31. Causes of Hypothyroidism
PRIMARY
Congenital
Agenesis
Ectopic thyroid remnants
Defects of hormone synthesis
Iodine deficiency
Dyshormonogenesis
Antithyroid drugs
Other drugs (e.g. lithium, amiodarone, interferon)
Autoimmune
Atrophic thyroiditis
Hashimoto's thyroiditis
Postpartum thyroiditis
Infective
Post-subacutethyroiditis

post-surgery

Post-irradiation
Radioactive iodine therapy
External neck irradiation
Infiltration
Tumour
SECONDARY
Hypopituitarism
Isolated TSH deficiency
34. Symptoms and Signs
35. Investigation of primary hypothyroidism
Serum TSH
The investigation of choice.
A high TSH level confirms primary hypothyroidism.
Serum T4
low free T4 level confirms the hypothyroid state.
Thyroid and other organ-specific antibodies .
36. Investigations of other abnormalities:
Anaemia.
Increased serum aspartatetransferaselevels, from muscle and/or liver
Increased serum creatinekinaselevels, with associated myopathy
Hypercholesterolaemia
Hyponatraemia due to an increase in ADH and impaired free water clearance.
37. Treatment
Replacement therapy with levothyroxine(thyroxine, i.e. T4) is given for life.
In the young and fit, 100 g daily is suitable.
thyroid function tests after at least 6 weeks on a steady dose
the aim is to restore T4 and TSH to well within the normal range
An annual thyroid function test is recommended .
38. Myxoedema coma
Severe hypothyroidism, associated with:
- confusion or even coma.
- hypothermia.
- severe cardiac failure.
- Hypoventilation.
- Hypoglycaemia.
- hyponatraemia.
patients require full intensive care.
39. Pathogenesis

Myxedema coma/crisis occurs most commonly in older women with long-standing, undiagnosed or undertreated hypothyroidism who experience an additional significant stress, such as infection, a systemic disease, certain medications, and exposure to a cold environment.

40. When hypothyroidism is long-standing, physiologic adaptations occur. 41. Reduced metabolic rate and decreased oxygen consumption result in peripheral vasoconstriction, which maintains core temperature. 42. The number of beta-adrenergic receptors is reduced, usually with preservation of alpha-adrenergic receptors and circulating catecholamines, causing beta/alpha-adrenergic imbalance, diastolic hypertension, and reduced total blood volume. 43. Myxedema coma/crisis is a form of decompensated hypothyroidism in which adaptations are no longer sufficient. 44. Essentially, all organ systems are affected.

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Lect 3-thyroid disorders