�ݺ�ߣ

OUTLINE
– Embryology and anatomy of the thyroid
– Physiology of the thyroid
– Investigations of thyroid diseases
– Causes of Hyperthyroidism
– Thyroid Cancers
September 10, 2022 gkg 2

EMBRYOLOGIC ORIGIN AND ANATOMY OF THE THYROID

STEPS OF THYROID HORMONE SYNTHESIS
• Involves:
– Iodide trapping
– Oxidation of iodide to iodine and iodination of tyrosine residues on
thyroglobulins (Tg)
– Coupling of iodothyronines to form T4 , T3 or rT3
– Hydrolysis to release free iodothyronines (T3 and T4) and mono- and
diiodotyrosines

TESTS OF THYROID FUNCTION
• Serum thyroid hormones:
– Serum TSH
– Thyroxine (T4) and tri-iodothyronine (T3)
– Thyroid autoantibodies

CONT…

THYROID IMAGING
• Chest and thoracic inlet radiography
• Ultrasound
• CT scan
• MRI and
• PET scanning
• Isotope scanning

FNAC
• Thy1- Non-diagnostic
• Thy2- Non-neoplastic
• Thy3- Follicular
• Thy4- Suspicious of malignancy
• Thy5 -Malignant

CLASSIFICATION OF THYROID SWELLINGS
 Simple goiter (euthyroid):
• Diffuse hyperplastic:
• Physiological
• Pubertal
• Pregnancy
• Multinodular goiter
 Toxic:
• Diffuse
Graves’ disease
• Multinodular
• Toxic adenoma
 Neoplastic:
• Benign
• Malignant
 Inflammatory:
– Autoimmune
• Chronic lymphocytic
thyroiditis
• Hashimoto’s disease
– Granulomatous
• De Quervain’s thyroiditis
• Fibrosing
• Riedel’s thyroiditis
• Infective
• Acute (bacterial thyroiditis,
viral thyroiditis, ‘subacute
thyroiditis’)
• Chronic (tuberculous,
syphilitic)
• Other
• Amyloid

THYROID ENLARGEMENT
• The normal thyroid gland is impalpable
• Goiter- generalized enlargement of the thyroid gland
• Solitary (isolated) nodule -a discrete swelling in one lobe with no palpable abnormality
elsewhere
• Dominant nodules- discrete swellings with evidence of abnormality elsewhere in the
gland

HYPOTHYROIDISM

• Deficiency in circulating levels of thyroid hormone
– Cretinism (fetal or infantile hypothyroidism)
• Dx:
• A hoarse cry
• Macroglossia and
• Umbilical hernia in a neonate
• Features of thyroid failure
• RX: thyroxine within a few days of birth
• Adult hypothyroidism
• Myxoedema -severe thyroid failure

CAUSES OF HYPOTHYROIDISM
• Primary (Increased TSH Levels):
– Hashimoto's thyroiditis
– RAI therapy for Graves' disease
– Postthyroidectomy
– Excessive iodine intake
– Subacute thyroiditis
– Medications: Antithyroids drugs,
lithium
– Rare: iodine deficiency,
dyshormogenesis
• Secondary (Decreased TSH Levels):
• Pituitary tumor
• Pituitary resection
or ablation
• Tertiary:
• Hypothalamic
insufficiency
• Resistance to thyroid
hormone

CLINICAL FEATURES
• The symptoms are:
• tiredness
• mental lethargy
• cold intolerance
• weight gain
• constipation
• menstrual disturbance
• carpal tunnel syndrome
• The signs of thyroid deficiency are:
• bradycardia
• cold extremities
• dry skin and hair
• periorbital puffiness
• hoarse voice
• bradykinesis, slow movements
• delayed relaxation phase of ankle
jerks

INVESTIGATION AND Rx
• Thyroid function tests:
–low T4 and T3
–high TSH (except in the rare event of pituitary failure)
–High serum levels of TPO antibodies are characteristic of
autoimmune disease
•Rx:
–Oral thyroxine (0.10–0.20 mg) as a single daily dose is curative

HYPERTHYROIDISM

DEFINITION
• Thyrotoxicosis
– the state of thyroid hormone excess
• Hyperthyroidism
– is the result of excessive thyroid function

CAUSES OF THYROTOXICOSIS

PRIMARY HYPERTHYROIDISM
• Graves' disease (60-80%)
• Toxic multinodular goiter
• Toxic adenoma
• Functioning thyroid carcinoma metastases
• Activating mutation of the TSH receptor
• Activating mutation of Gsa (McCune-Albright syndrome)
• Struma ovarii
• Drugs: iodine excess (Jod-Basedow phenomenon)

SECONDARY HYPERTHYROIDISM
• TSH-secreting pituitary adenoma
• Thyroid hormone resistance syndrome(occasionally),
• Chorionic gonadotropin-secreting tumors,
• Gestational thyrotoxicosis

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

• An Autoimmune disease
• 60-80% of thyrotoxicosis
• Age = 20-50 yrs
• M:F = 1:5
• Exact cause not known(
environment & genetics)
• Possible triggers:
– Postpartum period( 3х ↑ risk)
– Stress
– Smoking
– Excess Iodine intake
– Bact. / viral infection

WHAT CAUSES THE
HYPERTHYROIDISM?
• Sensitized T-helper cells stimulate B-lymphocytes  produce Abs
– TSI, TS Ab  stimulate TSH receptor
– Abs against TH receptor
– TPO Abs
• The coexisting thyroiditis can also affect thyroid function
• In the long term, spontaneous autoimmune hypothyroidism may develop in upto 15% of
Graves' patients.

CLINICAL FEATURES
• Signs and symptoms
– General SSx common to thyrotoxicosis by other causes
– SSx Specific to Graves’ disease

GENERAL TO THYROTOXICOSIS

CONT…
• There is increased tissue sensitivity to catecholamines in hyperthyroidism with an
increase in either the number of β-adrenoceptors or the second messenger response to
their stimulation

THYROID EXAMINATION
• Diffusely & smoothly enlarged thyroid
• Bruit – increased vascularity

GRAVES’ OPHTALMOPATHY
• Also called thyroid-associated ophthalmopathy as it occurs in the absence of Graves'
disease in 10% of patients
• Unilateral signs are found in up to 10% of patients
• The earliest manifestations are usually a sensation of grittiness, eye discomfort, and
excess tearing

GRAVES’ OPHTHALMOPATHY
• Proptosis – in 1/3 of patients
• may cause corneal exposure and
damage in severe cases
• Periorbital edema,
• Scleral injection,
• Chemosis
• Diplopia – in 5-10%, with severe
muscle swelling
 Papilledema, peripheral field defects,
and, if left untreated, permanent loss
of vision 2⁰ to compression of the
optic nerve at the apex of the orbit

"NO SPECS" SCORING SCHEME
 To gauge the extent and activity of the orbital change
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

THYROID DERMOPATHY
• In <5% of patients with Graves' disease
• Almost always in the presence of moderate or severe
ophthalmopathy
• Typical lesion - noninflamed, indurated plaque with a deep pink or
purple color & "orange-skin" appearance.

CONT…
• Most frequent over the anterior and lateral aspects of
the lower leg (pretibial myxedema)

THYROID ACROPACHY
• A form of clubbing found in <1% of patients with
Graves' disease
• Strongly associated with thyroid dermopathy
• without coincident skin and orbital involvement –
search for other causes of clubbing

LABORATORY FINDINGS
• ↓TSH , ± ↑Free T3 & T4
– 2-5% - only T3 ↑(T3 toxicosis) – in borderline iodine intake, & early
Graves’ ds
– T4 toxicosis – in excess iodine intake
• ¹²³I scan – homogenously enlarged gland with increased uptake , confirms
Dx
• Positive TPO or TSH-R Abs – in 75%
• TSH-R Abs & TSI diagnostic - in 90%

• A normal TSH excludes Graves' disease as a cause of
diffuse goiter

TREATMENT
• Reducing thyroid hormone synthesis
–Antithyroid drugs
• Reducing the amount of thyroid tissue
–Radioiodine (131I) treatment
–Thyroidectomy

TOXIC MULTINODULAR GOITER

CONT…
• TSH is low
• T4 – normal or minimally increased
• T3 – often elevated to a greater degree than T4
• Thyroid scan shows heterogeneous uptake

TREATMENT
• Antithyroid drugs, often in combination with beta blockers
– Often stimulates the growth of the goiter
–Spontaneous remission does not occur
– rendered euthyroid before operation
• Surgery provides definitive treatment of underlying thyrotoxicosis as well as goiter
• RAI - reserved for elderly, larger doses needed

• Thyrotoxicosis is usually mild
• A thyroid scan - definitive diagnostic test,
– Focal uptake in the hyper functioning nodule
– Diminished uptake in the remainder of the gland (activity of the
normal thyroid is suppressed)

TREATMENT
• Radioiodine ablation is usually the treatment of choice – for small nodules
• Surgical resection is also effective and is usually limited to enucleation of the
adenoma or lobectomy
• Medical therapy using antithyroid drugs and beta blockers can normalize
thyroid function
• Ethanol injection under ultrasound guidance

 Is life-threatening exacerbation of hyperthyroidism, accompanied by
• Fever
• Cardiac failure & arrhythmia
• Delirium
• Seizures
• Coma
• Vomiting
• Diarrhea
• Jaundice

PRECIPITATING FACTORS
• Acute illness (e.g., stroke, infection, trauma, diabetic ketoacidosis),
• Surgery (especially on the thyroid) & Trauma
• Radioiodine treatment of a patient with partially treated or untreated
hyperthyroidism

MANAGEMENT
• Aim of treatment:
– Intensive monitoring and supportive care
– Treatment of the precipitating cause
– Reduce thyroid hormone synthesis

HOW?
• O₂ supplementation
• Hemodynamic support
• Antipyretic & antibiotics
• Large doses of PTU (600 mg loading dose and 200–300 mg every 6 h)
• Saturated solution of potassium iodide (5 drops every 6 h), or ipodate or iopanoic acid
(0.5 mg every 12 h)
• Propranolol = 40–60 mg orally every 4 h
• Dexamethasone, 2 mg every 6 h

• Most common malignancy of the endocrine system
• Incidence of thyroid cancer (~9/100,000 per year) increases with age, plateauing after
about age 50
• M:F = 1:2
• history of childhood head or neck irradiation – a risk factor

PROGNOSTIC FACTORS
• Age (<20) or in older persons (>45) is associated with a worse prognosis
• Male sex is associated with a worse prognosis
• Histologic type – anaplastic ca has very poor prognosis & poor response to therapy

CLASSIFICATION
• Neoplasms can arise in each of the cell types that populate the gland
– Thyroid follicular cells –
 Papillary thyroid ca
 Follicular thyroid ca
 Hurthle cell ca
– Calcitonin-producing C cells – Medullary thyroid ca
– Lymphocytes - lymphomas
– Stromal and vascular elements
– Metastases from other sites

WELL-DIFFERENTIATED THYROID CA
• Papillary Thyroid Ca ( PTC )
• Follicular Thyroid Ca ( FTC )

PTC
• Accounts for 80% of all thyroid malignancies in iodine-sufficient areas
• >95% 10-year survival rate
• The predominant thyroid cancer in children and individuals exposed to external radiation.
• F : M = 2:1
• Mean age - 30 to 40 years
• Most are euthyroid
• slow-growing painless mass in the neck
September 10, 2022 gkg
58

PTC
• Dysphagia, dyspnea, and dysphonia -locally advanced invasive disease
• Lymph node metastases are common, especially in children and young adults, and may
be the presenting complaint.
• "Lateral aberrant thyroid" almost always denotes a cervical lymph node that has been
invaded by metastatic cancer

PTC
• Macroscopic findings- calcification, necrosis, cystic change
• Histologic variants – papillary, follicular, mixed
• Microscopic features
• Orphan Annie nuclei
• Psammoma bodies
• Multifocality is common – in 85%, ↑risk of cervical nodal metastasis
• Microcarcinoma - ≤ 1cm, no invasion

FTC
• 10% of thyroid cancers
• Common in iodine-deficient areas
• F : M = 3:1
• Mean age = 50 yrs
• Usu. - solitary thyroid nodules, long-standing goiter
• cervical LAP is uncommon
• In <1% of cases – SSx of thyrotoxicosis

• FNAC is unable to distinguish benign follicular lesions from follicular
carcinomas
• preoperative clinical diagnosis of cancer is difficult unless
distant metastases are present

MANAGEMENT
• All well-differentiated thyroid cancers should be surgically excised
• 131I ablation is necessary to eliminate remaining normal thyroid tissue and to treat
residual tumor cells.
• Patients should be placed on a low-iodine diet
• Levothyroxine suppression of TSH is a mainstay of thyroid cancer treatment

FOLLOW-UP
• Tg measurement - measurable levels indicate incomplete ablation or recurrent
cancer
• Whole-body scan should be performed about 6 months after thyroid ablation

ANAPLASTIC THYROID CANCER
• Poorly differentiated and aggressive cancer
• Prognosis is poor, most die within 6 months of diagnosis
• Uptake of radioiodine is usually negligible
• Chemotherapy has been attempted , but it is usually ineffective
• External beam radiation therapy can be attempted and continued if tumors
are responsive

MEDULLARY THYROID CARCINOMA
• Serum Calcitonin - a sensitive marker of MTC
• Serum CEA
• The management - primarily surgical
• Do not take up radioiodine
• External radiation treatment and chemotherapy may provide palliation in patients
with advanced disease

THYROID LYMPHOMA
• Often arises in the background of Hashimoto's thyroiditis
• Rapidly expanding thyroid mass
• Diffuse large-cell lymphoma is the most common type in the thyroid
• Often highly sensitive to external radiation
• Surgical resection should be avoided as initial therapy because it may spread disease

THYROID NEOPLASMS

SUMMARY

Classifiication of thyroid swelling
104

Indication for surgical intervention of
thyroid
109

Thyroid tumor shwarth staging
113

Thyroid tumor shwarth staging
114

Thyroid tumor PTC pronosis
119

Retrosternal Goiter
-It is prolongation of the lower pole of the thyroid behind
the sternum into the superior mediastinum, with blood supply
from inferior thyroid artery branch
-Clinical features: from pressure effect
1. Dyspnoea & cough
2. Dysphagia
3. Prominent veins occur at the root
of the neck
- Rx surgery indicated

�ݺ�ߣ

THYROID DISEASES BESTTTT.pptx

Convert to study guideBETA

More Related Content

THYROID DISEASES BESTTTT.pptx

Editor's Notes