Why are biopsies not usually performed on the thyroid gland?
What is the alternative?
Thyroid gland is very vascular
Do FNA instead
Describe the normal appearance of the thyroid gland?
Fleshy, mahogany coloured
Describe the origin of the cells of the thyroid gland?
C cells are neuroendocrine in origin
Rest are of epithelial origin
Describe the normal histology of the thyroid gland?
Round/oval follicles, various sizes
Epithelial cells line follicles
Follicles filled with colloid
Thin, fibrous septa with rich vascular supply
C cells (difficult to distinguish in H&E)
Describe the different histological appearance of inactive and active thyroid follicles?
Inactive: low cuboidal cells, follicle filled with colloid
Active: tall cuboidal/columnar cells, scalloping of colloid (cells taking up colloid)
Describe the metabolic symptoms of hypothyroidism?
cold, thickened skin
Describe the effects of hypothyroidism on the nervous system and the consequences of this?
Sympathetic nervous system underactivity > bradycardia, angina, slow reflexes, constipation, decreased mood and concentration
Which population is most affected by hypothyroidism?
What are the most common causes of hypothyroidism?
What is thyrotoxicosis?
Elevated circulating fT3 and fT4
Describe the metabolic effects of hyperthyroidism?
warm, flushed skin
Describe the effects of hyperthyroidism on the nervous system, and the consequences of this?
Sympathetic nervous system overactivity > palpitations, AF, cardiomegaly, tremor, anxiety, insomnia, diarrhoea
What are the major causes of thyrotoxicosis?
Hyperfunctioning toxic multinodular goiter
Describe the cause of a simple goiter?
Impaired synthesis of thyroid hormone > TSH elevation > thyroid growth stimulated
Describe the thyroid hormone levels in a simple goiter?
Usually euthyroid, with slightly high TSH
What is the most common cause of simple goiter?
Describe the histological appearrance of a simple goiter?
Crowded cells line follicles
Some follicles largr than others
Large colloid-filled cysts may be present
Describe what happens to the thyroid follicles in a simple goiter with:
a) TSH resolution
b) TSH persistence
a) Follicles incolute
b) Follicles rupture, haemorrhage or grow larger
Describe what can happen to a simple goiter over time?
Cycles of hyperplasia and involution > follicles can become large nodules > multinodular goiter
What can multinodular goiter progress to?
What are the consequences of this?
Nodules can be autonomous (secrete thyroid hormone without TSH) > toxic multinodular goiter
Patient may become hyperhtyroid
What is Pemberton's sign?
When does it occur?
Enlarged thyroid > compresses SVC when arms raised > blood backlog in SVC
Describe the histological appearrance of Hashimoto's thyroiditis?
Mononuclear inflammatory infiltrate: lymphocytes, plasma cells, germinal centres
Hurthle cells: thyroid cells with abundant, eosinophilic, granular cytoplasm
Increased interstitial connective tissue: fibrosis/scarring
Describe the gross pathology of Hashimoto's thyroiditis?
Enlatge at first > atrophic
Cut surface: firm, tan-yellow, pale, nodular
Describe the cause of Hashimoto's thyroiditis?
Breakdown of tolerance to thyroid tissues
Damage by: CD8 cytotoxic cell-mediated death, cytokine-mediated cell death, TSH-blocking Abs
Which population is most affected by Hashimoto's thyroiditis?
Describe the clinical presentation of Hashimoto's thyroiditis?
High Anti-g Abs
Very high Anti-TPO
High TSH, low fT4
Describe the triad of clinical findings in Graves disease?
1) Hyperhtyroidism due to diffuse, hyperfunctional enlargement of the thyroid
2) Infiltrative opthalmopathy > exopthalmos
3) Localised infiltrative dermopathy (pretibial myxoedoma)
What is the cause of Graves disease?
Stimulatory auto-Ab to TSH receptor
Describe the histological appearance of Graves disease?
Tall, crowded follicular cells > papillae
Diffuse hypertrophy and hyperplasia
Describe the gross pathology of Graves disease?
Diffuse symmetrical enlargement of thyroid
Soft, meaty cut surface