The document discusses the thyroid gland and thyroid disorders. It provides details on: - The anatomy and blood supply of the thyroid gland. - Thyroid follicles which are the functional units that secrete thyroid hormones like T4 and T3. - The two main thyroid disorders - hypothyroidism which is an underactive thyroid, and hyperthyroidism which is an overactive thyroid. - The most common causes of hypothyroidism including Hashimoto's thyroiditis, and the signs, symptoms, and treatment which involves thyroid hormone replacement. - Graves' disease as the most common cause of hyperthyroidism, along with its autoimmune pathogenesis and associated signs and

1. Thyroid Gland
Disorders

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.
2

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.  The thyroid gland is made up of closely packed sacs called
thyroid follicles.
 The structural and functional unit 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 and T3 present in colloid bound to a large protein called
thyroglobulin.
Thyroid Gland: introduction

5. Thyroid follicles

6. Development
 from the floor of the primitive pharynx during the third
week of gestation
 developing gland migrates along the thyroglossal duct to
reach its final location in the neck
 rare ectopic location of thyroid tissue at the base of the
tongue (lingual thyroid)
 occurrence of thyroglossal duct cysts along this
developmental tract

7.  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
Thyroid Gland: Introduction

8. Regulation of Thyroid Axis
 TSH –
 Thyrotrope cells of ant. Pituitary
 31 kDa hormone α and β subunits
 α subunit similar to LH, FSH and hCG
 Stimulated by TRH
 TSH, TRH supressed by Thyroxine

10. Actions of Thyroid Hormones
 Increase the body’s 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)

11. Thyroid disorders
 Hypothyroidism
 Underactive thyroid
 Hyperthyroidism
 Overactive thyroid
 Goiter
 Thyroid enlargement

12. 12
Hypothyroidism
Definition
 A clinical and biochemical syndrome that results
from a deficiency in thyroid hormone secretion
from thyroid gland or in the action

13. 13
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 60 years

14.  Iodine deficiency remains the most common cause
of hypothyroidism worldwide
 areas of iodine sufficiency, autoimmune disease
(Hashimoto's thyroiditis) and iatrogenic causes
(treatment of hyperthyroidism) are most common

15.  Primary Hypothyroidism
 Disease of the thyroid gland
 Secondary Hypothyroidism
 Hypothalamic-pituitary diseases (reduced
TSH)
Hypothyroidism

16. 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)

17. Causes of Hypothyroidism
 Autoimmune
 Atrophic thyroiditis
 Hashimoto's thyroiditis
 Postpartum thyroiditis
 Infective
 Post-subacute thyroiditis

18. Causes of Hypothyroidism
 Iatrogenic
 Radioactive iodine therapy
 External neck irradiation
 post-surgery
 Infiltration
 amyloidosis, sarcoidosis, hemochromatosis,
scleroderma

19. SECONDARY
 Hypopituitarism: tumors, pituitary surgery or irradiation,
infiltrative disorders, Sheehan's syndrome, trauma,
genetic forms of combined pituitary hormone deficiencies
 Isolated TSH deficiency or inactivity
 Hypothalamic disease: tumors, trauma, infiltrative
disorders, idiopathic

20. 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-Hodgkin’s lymphoma
 Other concomitant autoimmune diseases
 Endocrine and non-endocrine

21. Hashimoto Thyroiditis
Pathogenesis
 Immune systems reacts against a variety of thyroid
antigens
 Progressive depletion of thyroid epithelial cells which
are gradually 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

22. Symptoms and Signs

23. 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
TPO antibodies

24. Investigations of other abnormalities:
 Anaemia.
 Increased serum aspartate transferase levels, from
muscle and/or liver
 Increased serum creatine kinase levels, with associated
myopathy
 Hypercholesterolaemia
 Hyponatraemia due to an increase in ADH and impaired
free water clearance.

25. Treatment
 Replacement therapy with levothyroxine
(thyroxine, i.e. T4) is given for life.
 In the young and fit, 100 - 150 μg daily is suitable.
 thyroid function tests after at least 2 months 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 .

26. Subclinical Hypothyroidism
 biochemical evidence of thyroid hormone deficiency
in patients who have few or no apparent clinical
features of hypothyroidism
 guidelines do not recommend routine treatment
when TSH levels are below 10 mU/L
 low dose of levothyroxine (25–50 g/d) with the goal
of normalizing TSH

28. Myxoedema coma
 Severe hypothyroidism, associated with:
- confusion or even coma.
- hypothermia.
- severe cardiac failure.
- Hypoventilation.
- Hypoglycaemia.
- hyponatraemia.
 patients require full intensive care.

29.  occurs in the elderly
 usually precipitated by factors that impair respiration
 drugs (especially sedatives, anesthetics,
antidepressants)
 pneumonia, congestive heart failure, myocardial
infarction
 gastrointestinal bleeding
 cerebrovascular accidents
 Sepsis

30. Myxoedema coma
 Treatment:
 Levothyroxine as a single IV bolus of 500 g, which
serves as a loading dose-50–100 ug/d
 oxygen (by ventilation if necessary)
 monitoring of cardiac output and pressures
 gradual rewarming
 hydrocortisone 100 mg i.v. 8-hourly
 glucose infusion to prevent hypoglycaemia.

32.  Thyrotoxicosis - as the state of thyroid hormone
excess
 Hyperthyroidism - result of excessive thyroid function
 major etiologies of thyrotoxicosis are hyperthyroidism
caused by Graves' disease, toxic MNG, and toxic
adenomas

33. Causes of hyperthyroidism
Common
 Graves' disease (autoimmune)
 Toxic multinodular goitre
 Solitary toxic nodule/adenoma

34. Causes of Thyrotoxicosis
Primary hyperthyroidism
 Graves' disease
 Toxic multinodular goiter
 Toxic adenoma
 Functioning thyroid carcinoma metastases
 Struma ovarii
 Drugs: iodine excess (Jod-Basedow phenomenon)

35. Thyrotoxicosis without hyperthyroidism
 Subacute thyroiditis
 Silent thyroiditis
 Other causes of thyroid destruction: amiodarone,
radiation, infarction of adenoma
 Ingestion of excess thyroid hormone (thyrotoxicosis
factitia) or thyroid tissue

36. Secondary hyperthyroidism
 TSH-secreting pituitary adenoma
 Chorionic gonadotropin-secreting tumorsa
 Gestational thyrotoxicosisa

37. Graves' disease
 The most common cause of hyperthyrodism
 It is an autoimmune disorder. where the thyroid is
overactive, producing an excessive amount of thyroid
hormones
 More common in adults -between 20 and 50 years
 Can be familial and associated with other autoimmune
diseases
 Characterized by hyperthyroidism, ophthalmopathy with
exophthalmos and dermopathy (pretibial myxedema)

38. Graves’ Disease
Autoimmune disease with breakdown of helper-T-cell tolerance
Excessive production of thyroid autoantibodies:
Thyroid-stimulating antibody (TSI)
Antibodies bind to the TSH receptor of the follicular cell
Stimulation of the cell resulting in:
Increased levels of thyroid hormones &
Hyperplasia of the thyroid gland
Hyperthyroidism and Thyroid gland enlargement

39. Hyperthyrodism
 Clinical features: due to
 Hypermetabolic state
 Overactivity of sympathetic nervous system

40. Symptoms
 Weight loss
 Increased appetite
 Irritability
 Tremor
 Goiter
 Restlessness
 Stiffness
 Muscle weakness
 Breathlessness
 Palpitation
 Heat intolerance
 Excessive sweating
 Itching
 Thirst
 Vomiting
 Diarrhoea
 Oligomenorrhoea
 Loss of libido

41. Signs
 Tremor
 Irritability
 Psychosis
 Tachycardia or atrial fibrillation
 Warm peripheries
 Systolic hypertension
 Cardiac failure

42. Signs
 Lid lag
 Proximal myopathy
 Proximal muscle
wasting
 Onycholysis
 Palmar erythema

43. Eye disease

44. Graves' Ophthalmopathy
 earliest manifestations - sensation of grittiness, eye
discomfort, and excess tearing
 most serious manifestation is compression of the
optic nerve at the apex of the orbit, leading to
papilledema; peripheral field defects; and, if left
untreated, permanent loss of vision

45.  0 = No signs or symptoms
 1 = Only signs (lid retraction or lag), no symptoms
 2 = Soft-tissue involvement (periorbital edema)
 3 = Proptosis (>22 mm)
 4 = Extraocular-muscle involvement (diplopia)
 5 = Corneal involvement
 6 = Sight loss

46.  Thyroid dermopathy/pretibial myxedema - most
frequent over the anterior and lateral aspects of the
lower leg
 Thyroid acropachy - clubbing found in <1% of
patients with Graves' disease

48. Investigation
 Thyroid function test:
 Serum TSH is suppressed in hyperthyroidism .
 Diagnosis is confirmed with a raised free T4 or T3
 . Measurement of TPO antibodies or TBII may be
useful if the diagnosis is unclear clinically

50. Treatment
Antithyroid drugs:
1. Carbimazole.
2. Propylthiouracil.
 These drugs inhibit the formation of thyroid hormones
 common side effects - rash, urticaria, fever, and
arthralgia
 Rare but major side effects include hepatitis; an
SLE-like syndrome; and, most important,
agranulocytosis

51. Treatment
 Radioactive iodine
 RAI accumulates in the thyroid and destroys the gland
by local radiation.
 It takes several months to be fully effective.

52. Treatment
 Surgery:
 subtotal thyroidectomy
 Only in patient who have previously been rendered
euthyroid.

53. Goiter
 Goiter refers to an enlarged thyroid gland
 Biosynthetic defects, iodine deficiency, autoimmune
disease, and nodular diseases can each lead to
goiter
 diffuse nontoxic goiter - diffuse enlargement of the
thyroid occurs in the absence of nodules and
hyperthyroidism
 Worldwide, diffuse goiter is most commonly caused
by iodine deficiency and is termed endemic goiter

54. Congenital Thyroid Diseases
 Agenesis /Aplasia
 Hypoplasia
 Accessory or aberrant thyroid glands
 Thyroglossal duct cyst

55. 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

56. 
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