Thyroid Pathology Flashcards by Srishti D

How much does the normal thyroid gland weigh?

20 g +/- 5-10 g

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Why can’t you do a biopsy of the thyroid gland?

Very vascular

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Can you do a fine needle aspirate of the thyroid gland?

Yes

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What is the colour of the thyroid gland?

Fleshy

Mahogany

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What does thyroid stimulating hormone (TSH) stimulate?

Increased proliferation
Increased cell size
Increased calcitonin function
Increased thyroid hormone synthesis and release

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Where are the follicular cells in the thyroid gland?

Surround colloid

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What is the colloid?

Glycoprotein mix

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What does the colloid contain?

Thyroglobulin

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Where are the C cells?

In interstitial space

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What do the C cell secrete?

Calcitonin

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What is calcitonin involved in?

Calcium metabolism

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What is normal thyroid histology with H&E stain?

Round to oval follicles of various sizes
Lined by thyroid epithelial cells
Filled with colloid = pink
Thin fibrous septa with rich blood supply

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What is the origin of C cells?

Neuroendocrine

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What does an inactive thyroid gland look like histologically?

Low cuboidal cells

Follicle filled with colloid

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What does an active thyroid gland look like histologically?

Tall cuboidal to columnar cells

Scalloping of colloid

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Does a hypo-/eu-/hyperthyroid state give a definitive diagnosis?

No, as possible in any condition

Give indication of disease

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What is hypothyroidism?

Inadequate circulating T3 and T4

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What does inadequate T3 and T4 lead to?

Hypometabolic state
- Cold intolerance
- Cold thickened skin
- Alopecia
- Weight gain with decreased appetite
- Fatigue
Autonomic effects
- Bradycardia
- Angina
- Slow relaxing reflexes
- Constipation
- Low mood and concentration

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What does hypothyroidism in children lead to?

Developmental abnormalities

Cretinism

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What are the hormone test results generally in hypothyroidism?

Increased TSH

Decreased T4

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What is the difference between thyrotoxicosis and hyperthyroidism?

Thyrotoxicosis = too much thyroid hormone circulating
Hyperthyroidism = thyroid gland working too hard to make hormone

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What do elevated circulating levels of T3 and T4 lead to?

Hypermetabolic state
- Heat intolerance
- Warm flushed skin
- Fatigue
- Weight loss with increased appetite
- Osteoporosis
Autonomic effects
- Palpitations
- Arrhythmias
- Cardiomyopathy
- Tremor
- Anxiety
- Insomnia
- Emotional lability
- Diarrhoea
- Lid lag

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What are the hormone tests generally in thyrotoxicosis?

Decreased TSH

Increased T4

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What is a goitre?

Thyroid bigger than usual

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Who dos goitre affect more: males or females?

Females

What does a diffuse non-toxic (simple) goitre reflect?

Impaired synthesis of thyroid hormone

What is the most common cause of impaired synthesis of thyroid hormone?

Dietary iodine deficiency

What happens to TSH in response to low thyroid?

Increases

Are people with a simple goitre usually hypothyroid, euthyroid, or hyperthyroid?

Euthyroid - TSH normal to slightly high - T4 generally normal

Will the goitre regress if TSH and thyroid hormones return to normal>

Yes

Where is dietary iodine deficiency most common?

Mountainous areas away from sea

When does goitre become endemic?

If more than 10% of population has it

What are other causes of simple goitre?

Congenital biosynthetic defects | Goitrogens in certain foods

What does a simple goitre look like histologically?

Hyperplastic Follicles lined by crowded cells Some follicles larger than others Can have large colloid-filled cysts

What can happen to thyroid follicles with persistent high TSH?

Some can rupture/haemorrhage | Others grow larger

How does a simple goitre become multinodular?

Cycles of hyperplasia and involution > some follicles become large nodules > others rupture and fibrose

How does a multinodular goitre feel on palpation?

Hard and fibrosed

What might be seen histologically with a multinodular goitre?

Haemosiderin Calcification Cholesterol clefts

Is it common for a multinodular goitre to become a toxic multinodular goitre?

What happens in toxic multinodular goitre?

Nodules can become autonomous

Are patients with a multinodular goitre hypothyroid, euthyroid, or hyperthyroid?

Can become hyperthyroid

What is the management of a simple goitre?

Iodine/thyroid hormone replacement therapy Surgery to relieve compressive symptoms and cosmetic effect If autonomous nodule, assess if malignant > remove

How long does a diffuse goitre take to regress?

3-6 months

How long does a multinodular goitre take to regress?

Less than 1/3 regress

What is the histopathology of Hashimoto thyroiditis?

Mononuclear inflammatory infiltrate - Lymphocytes with T cells = B cells - Plasma cells Germinal centres Thyroid cells have abundant, eosinophilic granular cytoplasm = Hurthle cells Increased interstitial connective tissue - Chronic inflammation > fibrosis/scarring

What is the gross pathology of Hashimoto thyroiditis?

``` Enlarged at first > eventually atrophies Cut surface - Firm - Pale - Fibrotic - Somewhat nodular - Tan-yellow colour ```

What causes the damage in Hashimoto thyroiditis?

CD8 T cell mediated cell death Cytokine mediated cell death Antibody dependent cell mediated cytotoxicity

What causes further reduced thyroid function in Hashimoto thyroiditis?

TSH-blocking Abs

What is the prevalence of Hashimoto thyroiditis?

5-10% of women with increasing age

What is the most common autoimmune disease?

Hashimoto thyroiditis

What is the female predominance of Hashimoto thyroiditis?

10-20:1

Is there a strong genetic component with Hashimoto thyroiditis?

Yes

Is there an associated susceptibility to other autoimmune conditions in Hashimoto thyroiditis?

Yes

Which cancer is there an associated risk with in Hashimoto thyroiditis?

B-cell non-Hodgkin lymphoma

What is the clinical presentation of Hashimoto thyroiditis?

``` Gradual onset of hypothyroidism and/or goitre Increased TSH Decreased T4 Increased thyroglobulin Abs Massive increase in anti TPO Abs Fine needle aspirate will show - Hurthle cells - Mixed population of lymphocytes ```

What is the management of Hashimoto thyroiditis?

Thyroxine replacement | Monitor closely if elderly or pregnant

What are the clinical features of Graves disease?

Hyperthyroidism due to diffuse, hyperfunctional enlargement of thyroid Infiltrative ophthalmology > exophthalmos Localised infiltrativ dermopathy in minority of patients

What is the cause of Graves disease?

Stimulatory Abs to TSH receptor - Thyroid stimulating Igs (TSI) - Thyroid growth-stimulating Igs - TSH-binding inhibitor Igs - Can stimulate/inhibit

What is the histopathology of Graves disease?

``` Follicular cells tall and more crowded - Diffuse hypertrophy and hyperplasia - May form papillae in follicle lumen Widespread excessive scalloping of colloid - Colloid paler staining Lymphocytic infiltrates - Mostly T cells - Sometimes germinal centres ```

What is the gross pathology of Graves disease?

Diffuse symmetrical enlargement | Cut surface soft and meaty

What is Hashitoxicosis?

Thyrotoxic Hashimoto disease | If Abs attack thyroid gland very specifically > follicles rupture > release thyroid hormones

What is the prevalence of Graves disease?

0.5-2%

What is the female predominance of Graves disease?

5-8:1

What is there an association with in Graves disease?

Genetics | Association with smoking

What is the most common cause of hyperthyroidism?

Graves disease

What are the hormone and serology results in Graves disease?

Decreased TSH Increased T4 Increased Anti TPO Abs Increased TSI = diagnostic

Why do you get ophthalmopathy in Graves disease?

Retro-orbital hydrophilic mucopolysaccharides > oedema > lymphocytes, fibrosis, and fat

What is the role of fibroblasts in exophthalmos in Graves disease?

Target and effector cells Express TSH-like Ags Produce more hyaluronic acid Transform into adipocytes

What eye problems can exophthalmos cause?

``` Problems with - Cornea - Optic nerve - Venous drainage - Cosmetic Diplopia ```

What is the management of Graves disease?

``` Reduce sympathetic overactivity - Beta blockers Reduce elevated thyroid function - Antithyroid drugs; eg: carbimaozole - 18 month course results in remission in ```