Describe the histology of the thyroid gland
- Comprises of follicles
- Each follicle surrounded by flat to cuboidal follicular epithelial cells
- Colloid contains thryoglobulin
- Scattered amoing the follicles is parafollicular (C-cells) cells
What is thyroglobulin ?
The protein on which T3 and T4 are synthesised
What do C-cells secrete ?
What are some of the common pathologies affecting the thyroid gland ?
- Hyperthyroidism/ Thyrotoxicosis
What are the antibodies commonly seen in Graves disease causing hyperthryoidism ?
TSH receptor antibodies
Normal function thyroid
What is the most common thyroid disease ?
Non-toxic nulti-nodular goitre
What is non-toxic mutli-nodular goitre ?
- Nodular enlargement of the thyroid gland
- Affected individuals can be either euthyroid or hypothyroid
How does non-toxic multi-nodular goitre arise ?
- Result from absolute or relative iodine deficiency
- Results in increased TSH secretion
- This induces hyperplasia in an attempt to increase thyroid hormone output
- These increased demands are usually intermittent and the gland therefore undergoes cycles of growth and shrinkage
- End result is nodules of varying size with fibrosis, haemorrhage and focal inflammation seen
What are some of the complications of mutli-nodular goitres ?
- May produce symptoms suggestive of tumour
- Can cause compression of trachea, oesophagus, or recurrent laryngeal nerve
What are some of the histological features seen in graves disease causing hyperthroidism ?
- Gland is hyperplastic and hyperaemic
- Thyroid epithelium is hyperplastic and there is little coloid storage
What antibody is usually present in hashimotos disease causing hypothyroidism
What are the typical histological features of hashimotos thyroiditis ?
Gland is widely infiltrated by lymphocytes, plasma cells, macrophages
Thyroid follicular cells are enlarged with eosinophilic granular cytoplasm due to accumulation of mitochondria
Define what a goitre is
Any enlargement of the thyroid gland
What are the main types of goitres and how does a goitre occur ?
Diffuse and mutli-nodular goitres
- Diffuse = entire goitre becomes enlarged
- Multi-nodular = lots of nodules of enlargement
Occur due to Reduced T3 / T4 production causing a rise in TSH, stimulating gland enlargement
What are the usual thyroid function results for diffuse goitres ?
T3 / T4 normal but TSH high or upper limit of normal due to increased TSH compensating
Where are the parathyroid glands located ?
You have 4 (2 upper and 2 lower) located posterior to the thyroid gland
What are the 2 main cell types which the parathyroid glands are made up of
Chief cells and Oxyphil cells
What is the function of chief cells in the parathyroid glands ?
- Secrete PTH
- Act on Ca homeostasis (regulates calcium levels)