Thyroid Pathology Flashcards
How much does the normal thyroid gland weigh?
20 g +/- 5-10 g
Why can’t you do a biopsy of the thyroid gland?
Very vascular
Can you do a fine needle aspirate of the thyroid gland?
Yes
What is the colour of the thyroid gland?
Fleshy
Mahogany
What does thyroid stimulating hormone (TSH) stimulate?
Increased proliferation
Increased cell size
Increased calcitonin function
Increased thyroid hormone synthesis and release
Where are the follicular cells in the thyroid gland?
Surround colloid
What is the colloid?
Glycoprotein mix
What does the colloid contain?
Thyroglobulin
Where are the C cells?
In interstitial space
What do the C cell secrete?
Calcitonin
What is calcitonin involved in?
Calcium metabolism
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
What is the origin of C cells?
Neuroendocrine
What does an inactive thyroid gland look like histologically?
Low cuboidal cells
Follicle filled with colloid
What does an active thyroid gland look like histologically?
Tall cuboidal to columnar cells
Scalloping of colloid
Does a hypo-/eu-/hyperthyroid state give a definitive diagnosis?
No, as possible in any condition
Give indication of disease
What is hypothyroidism?
Inadequate circulating T3 and T4
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
What does hypothyroidism in children lead to?
Developmental abnormalities
Cretinism
What are the hormone test results generally in hypothyroidism?
Increased TSH
Decreased T4
What is the difference between thyrotoxicosis and hyperthyroidism?
Thyrotoxicosis = too much thyroid hormone circulating Hyperthyroidism = thyroid gland working too hard to make hormone
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
What are the hormone tests generally in thyrotoxicosis?
Decreased TSH
Increased T4
What is a goitre?
Thyroid bigger than usual
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?
No
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
