thyroid pdf - dr nadia

Disorders of Thyroid

Hyperthyroidism

Hypothyroidism

Thyroiditis

Diffuse multinodular Goiter

Neoplasms – adenoma/carcinoma

Congenital – Thyroglossal cyst/duct

Goiter

It is a diffuse or focal enlargement of the thyroid gland

Caused by: 1- Colloid goiter. 2- Grave’s disease. 3- Thyroiditis. 4- Tumors

Colloid goiter

most cases start as diffuse enlargement with nodularity development at later

stages

They represent compensatory hyperplasia of follicular epithelium

secondary to decreased thyroid hormone production

Diffuse-Multinodular goiter

Pathophysiology

Endemic & sporadic types

Endemic: Cassava – thiocyanate – iodide transport

- Sporadic: rare, females, young and usually of unclear cause. (may be

associated mild defect, iodine deficiency and physiological needs

- When there is low T3 and T4 there will be an increase of TRH & TSH that
induce secretion of thyroid hs associated with enlargement of thyroid gland by
hypertrophy and hyperplasia of follicular epithelium at earlier stages diffuse and

by time nodular

Stages:

Hyperplastic stage & Colloid stage

due to uneven hyperplasia and accumulation

of colloid as a result of tension and stress that lead to rupture of follicles

CLINICALLY:

1-Huge size result in dysphagia, airway obstruction, chocking sensation and
stridor. SITE as retrosternal extension causing superior vena cava syndrome with

vein enlargement, tachycardia and heart failure

2- Rarely toxic hyperthyroidism plummer syndrome

3- Mass effect and misdiagnosed as tumor need US, isotope scanning, FNAC, CT

scan and MRI

Morphology:

Grossly: at early stages symmetric and diffusely enlarges the thyroid gland
and in late stages there is multiple nodules on cut surfaces. Some nodules
show cystic degeneration, hemorrhage, fibrosis, and calcification.

Microscopy: show randomly sized colloid filled follicles lined by flattened cells
due to pressure of colloid with focal areas of hyperplasia, fibrosis, cystic
changes, necrosis & hemorrhage present as hemosiderin laden macrophages

Hyperthyroidism

Thyrotoxicosis it is a hypermetabolic state encountered much more often in
females caused by High free T3/T4 in the blood.

CAUSES: COMMON:

1- Diffuse toxic hyperplasia (Graves)

2- Toxic multinodular goiter

3- Toxic adenoma.

UNCOMMON CAUSES:

1- Thyroiditis

2- Functioning thyroid carcinoma

3- TSH secreting pituitary adenoma

4- Iatrogenic.

5- Struma ovarii.

6- Choriocarcinoma and hydatidiform mole.

Clinical features:

- Nervousness, palpitations, rapid pulse, fatigability, muscular weakness, weight
loss with good appetite, diarrhea, heat intolerance, warm skin, excessive
perspiration, emotional liability, menstrual changes, fine tremor of the hand,

eye changes and enlargement of the thyroid gland

- Cardiac manifestations: tachycardia, arrhythmias, especially fibrillation or SVT,
cause is obscure but more prone to occur in old age group

Graves Disease

Common (2%F)

Females, 20-40y, Autoimmune, associated with other autoimmune diseases

HLA B8 and DR3.

Triad of clinical features,

Hyperthyroidism

Exopthalmos and retraction of the upper eyelid.

Pretibial myxedema.

- Ab to TSH receptor – thyroid stimulating antibody, thyrotropin binding
inhibitor immunoglobulin are responsible for hyperfunction.

- Thyroid growth immunoglobulin responsible for hyperplasia.

Micro: Diffuse hyperplasia, tall columnar cells, papillary folds

& Scalloped, pale, scanty colloid.

Hypothyroidism

Cretinism / Myxedema – Low T3/T4, High TSH

Causes:

Hashimoto’s thyroiditis – autoimmune

Iodine deficiency

Drugs – PAS, iodides, lithium

Developmental – Atrophy, hypoplasia Pituitary disorders

Radiation/Surgery

Cretinism (child)

Impaired CNS & bone growth

Mental retardation

Short stature

- Coarse facial features

Protruding tongue

Umbilical hernia

Myxedema (adult)

- Slow physical and mental activity

Cold intolerance

Over weight

- Low cardiac output

- Constipation and decreased sweating

- Cool pale thick skin

Thyroiditis

Some are ill defined as interstitial th.

- Some are rare as palpation th. And suppurative (always blood borne).

- Reidel’s fibrous thyroiditis of unknown etiology manifested as atrophy and
hypothyroidism with fibrous adhesions.

are

Common types

1- Hashimoto’s thyroiditis,

2- subacute lymphocytic thyroiditis

3- subacute granulomatous

Hashimoto Thyroiditis

Common non endemic goitre.

females more common 45-65y.

Autoimmune disease with genetic basis HLA-DR5, DR3.

( defect in thyroid specific suppressor T cells lead to emergence of T helper
cells against specific thyroid antigens which cooperate with B cells lead to
formation of auto-antibodies as Ab to thyroid peroxidases formerly known
as antimicrosomal Abs & Anti- thyroglobulin antibody)

Initial hyperthyroidism and in long standing cases hypothyroidism.

High risk of B cell lymphoma.

Firm diffuse goiter.

Grossly:

Follicle atrophy with lymphocytic infiltration.

Microscopy:

Hürthle cells – eosinophilic cells.

Fibrosis & destruction of follicular tissue.

Granulomatous Thyroiditis:

Subacute or DeQuervain thyroiditis.

Less common, Females, 30-60 years

- Pain, fever, fatigue, myalgia.

- Post viral syndrome.

- Genetic association - HLA B35

Patchy microabscess, granulomas with giant cells.

- Hyperthyroidism.

Heals with normal thyroid function.

Subacute lymphocytic thyroiditis

Foci of lymphocytic infiltration with mild fibrosis.

-Obscure origin but may be an autoimmune in origin.

Thyroid Cancer

Classification:

Epithelial cell tumors

Differentiated

Papillary (75- 80%)

Follicular (10-20%)

Undifferentiated

Anaplastic (3-5%)

Parafollicular (C- cell) tumors

Medullary ( 5%)

Lymphoma (1-2%)

3- Others

Neoplasms of Thyroid

Adenoma – Follicular adenoma – hot

Papillary Carcinoma – 75-80%

Follicular carcinoma - 10-20%

Medullary carcinoma – 5%

Anaplastic carcinoma - <5%

Neoplasms of Thyroid:

Usually solitary, benign.

Good prognosis - <1% cancer mort.

May be functional – hot nodule.

Malignancy - Infiltration – fixation, hoarseness, recurrent laryngeal nerve
damage.

Clinical Presentation:

Thyroid nodule (most common)

Cervical lymph node(s)

Local compressive symptoms

Distant metastasis

Thyroid dysfunction

Thyroid Nodules:

- Prevalence: Physical Exam 4-7%

Ultrasound

30%

Autopsy

50%

- Incidence increases with age

Thyroid Nodules

(

Cont’d

)

Most thyroid nodules are BENIGN

A thyroid nodule has 5-12% malignancy rate

History of radiation increases the chance of malignancy to 30-50%

Evaluation:

History

Physical Examination

Laboratory Evaluation

TSH and FNAC

Imaging Studies

NOT VERY HELPFUL

HISTORY:

Age < 20 or > 50

Head or neck irradiation

Family history

Male sex

Recent growth

Pressure symptoms

PHYSICAL EXAMINATION:

Hard non tender nodule

Nodule of different consistency within MNG

Fixed nodule

Cervical lymphadenopathy

Immobile vocal cord

Ultrasonography:

Generally has a minor role in the evaluation of thyroid nodules

Palpable nodules do not need ultrasound

Small non-palpable nodules (<1cm) are generally unimportant even if
malignant

Cystic nodules can be malignant

FNA:

The most important test in the evaluation of a thyroid nodule

Has an overall sensitivity of 83-98% and specificity of 92-100%

Complications are very rare and usually minor

Radionucleotide Scans:

Most thyroid nodules are cold (95%)

Most cold nodules are benign (80-85%)

Hot nodules are usually functioning and can be detected by TSH (suppressed)

Warm nodules can be malignan

Radioactive iodine:

is concentrated from the blood by thyroid follicular cells, allowing correlation of
anatomic features with thyroid function. Decay of radioactive iodine is detected
as dark spots on the scan. A normal thyroid gland shows diffuse moderate
iodine uptake in the right and left lobes and isthmus. Graves disease is
characterized by diffuse increased uptake. Multinodular goiter most often
shows patchy, irregular uptake with some nodules hyperfunctional compared to
normal (dark, or "warm," on scan) and other nodules hypofunctional (pale, or
"cold"). The focal rounded defect lacking uptake (cold nodule) is characteristic
of thyroid neoplasms and cysts. A focal rounded area of increased uptake that
suppresses the remaining thyroid gland (hot nodule, not pictured) is most often

a hyperfunctional follicular adenoma or goiter nodule

Evaluation (Summary):

Most thyroid nodules are benign

TSH determines the thyroid functional status

Thyroid scanning and U/S are generally not helpful

FNA is the most useful diagnostic procedure

Adenoma

Follicular common, rarely Papillary

Compact follicles (large in MNG)

Solitary, rarely Functional or hot.

Centre may show necrosis/hem.

Well capsulated.

Compressed normal gland

Thyroid Carcinoma

Uncommon – child – elderly.

Common - Papillary adenocarcinoma.

Associated with radiation exposure, especially during the first 2 decades.

Type

Age

Spread

Prognosis

Papillary

Young <45y

Lymph

Excellent

Follicular

Middle age

B.V.

Good

Anaplastic

Elderly

Local

Poor

Medullary

Elderly

Familial

All

variable

Papillary Carcinoma

Most common cancer – 75-80%

Idiopathic, Radiation, Gardner & Cowden syndromes.

Papillary folds, Psammoma bodies, Orphan-Anne nucleus.

98% 10 year survival when localized.

Conclusions:

Hyperthyroidism

Graves, thyrotoxicosis, LATS

Hypermetabolism, high T3/T4, low TSH

Thyrotoxicosis

Antithyroglobulin, anti microsomal

Hypometabolism, Low T3/T4, high TSH

Multinodular goitre – low iodine

Neoplasms

Follicular adenoma – capsulated, single

Carcinoma: Papillary follicular, medullary, anaplastic