L14: Thyroid disease Flashcards
What are the types of cells in a thyroid gland
- C-cells: produce calcitonin which are involved in calcium homeostasis
- colloid cells: store thyroid hormones
What is the HPR axis ?
Hypothalamus secretes TRH to the anterior pituitary gland
Anterior pituitary gland secretes TSH to the thyroid gland
Thyroid gland secretes T3 and T4 to the cardiovascular, digestive and neurological system
T3 and T4 inhibit the hypothalamus and anterior pituitary gland via negative feedback
What is hyperthyroidism
High levels of thyroid hormone in the body
What is hypothyroidism
Low levels of thyroid hormone in the body
What are the 3 main causes of hyperthyroidism
- Graves’ disease
- Thyroiditis (inflammation)
- toxic nodular goitre
What is graves disease
An autoimmune disease causes by antibodies binding to TSHR receptors on follicular cells which cause the continuous secretion of thyroid hormones
Symptoms of hyperthyroidism
Cardiovascular:
- tachycardia
- atrial fibrillation
Digestive:
- weight loss
- diarrhoea
Neurological
- anxiety
- tremor
- myopathy
Eye:
- double vision
- staring eyes
- itching
Diagnosis of graves disease
- serum TSH levels
- antibodies of TSH receptors
- isotope uptake scans
Treatment of hyperthyroidism
- surgery removal of thyroid gland
- drugs of carbimazole and proythiouracil which block thyroperoxidase enzyme to produce thyroid hormones
How are thyroid hormones produced
- TSH made by the anterior pituitary gland binds to TSH receptor on follicular cells of the thyroid gland
- I/NA symporter takes in iodine from the blood
- idoine is taken into the calloid
- idoine residues are joined to thyroglobulin precursor by thryoperoxidase enzyme to form MIT and DIT
- MIT+DIT= T3, DIT+DIT=T4
- thyroid hormones are released by exocytosis
What happens to T4
Mono-iodination occurs with T4 so an idioine is removed to give the active hormone of T3.
This occurs by deiodinase enzyme which is created in the peripheral tissue
What is T4 and T3 bound to in the blood
- TBG
- Albumin
- transthyretin
- rest of it is free
What are the main causes of hypothyroidism
- iodine deficiency
- treatment of hyperthyroidism
- hashimoto thyroidits
What is hashimoto thyroiditis
An autoimmune disease where nflammation of the thyroid gland where it becomes swelled up then shrinks after
Where is iodine deficiency most common
In mountainous areas where there is not enough fish to eat
Symptoms of hypothyroidism
Cardiovascular:
- bradycardia
- heart failure
- pericardial effusion
Digestive:
- weight gain
- constipation
Neurological
- psychosis
- depression
Skin
- vitiligo
- Myxoedema
Diagnosis of hypothyroidism
- serum tsh levels
Treatment of hypothyroidism
- levothyroxine
What is a goitre
Enlargement of the thyroid gland
Why does a goitre or nodule have to be assessed
Goitre and nodules are common but you can get rare cancers present. You need to identify patients with malignancy
How to asses a nodule and goitre
Asses thyroid function
- TSH levels
Asses size
- symptoms
- x-ray
- MRI
- respiratory flow loop
Asses pathology
- radionucleide scanning
- ultrasound scanning
What are the types of thyroid cancer
Medullary carcinoma- from c-cells
Papillary and follicular carcinoma- from follicular cells
Papillary and follicular can differentiate to become anaplastic which is the most extreme type of thyroid cancer
Treatment of thyroid cancer
- surgery to remove gland
- Radioiodine ablation
- thyroxine suppression
What is thyroxine
The name of t4
