Thyroid Flashcards
(35 cards)
Explain the release of T3 and T4
- Hypothalamus releases TRH (thyrotropin releasing hormone) which acts on the anterior pituitary gland
- Anterior pituitary gland releases TSH (thyroid stimulating hormone)
- Thyroid gland releases T3 and T4 (negative feedback on the anterior pituitary and the hypothalamus)
What is the effect of T3 and T4?
- Increased metabolism (increases oxygen consumption and therefore heat)
- Growth and development
- Increased catecholamine effect
How does T3 carry about its effects?
It enters the nucleus and then binds with coregulators and leads to changes in gene transcription
What is Grave’s disease?
- Long acting thyroid stimulator - autoimmune stimulation of the thyroid
- Causes hypertrophy of the thyroid and hyperthyroidism
What is Hashimotos?
- Autoimmune destruction of thyroid
* Atrophy of the thyroid and hypothyroidism
What are the causes of hypothyroidism?
•Pituitary - hypopituitarism
•Thyroid:
- Thyroidectomy
- Post radioactive iodine ablation
- Autoimmune: Hashimoto’s, blocking TSH receptor antibodies, postpartum thyroiditis
- inborn errors: congenital hypothyroidism
What are the signs of neonatal hypothyroidism
- Cretinism
- Coarse facial features
- Macroglossia
- Large fontanelles
- Umbilical hernia
- Mottled, cool, and dry skin
- Developmental delay
- Pallor
- Myxoedema
- Goitre
What are the causes of congenital hypothyroidism?
•Thyroid degenesis: TSH receptor •Dyshormonogenesis - thyroid peroxidase - thyroglobulin - sodium iodide symporter - pendrin (pendred syndrome)
What are the signs/symptoms of hypothyroidism?
- Cold intolerance
- Weight gain and decreased apetitie
- Oedema
- Depression
- Low heart rate and BP
- Muscle cramps, myalgia
- Constipation (decreased GI motility)
- Skin pale, thick and dry
- Hair coarse and thick
What are the symptoms of hyperthyroidism?
- Heat intolerance
- Weight loss and loss of muscle mass
- Irritability, restlessness, insomnia
- Exopthalmos in graves disease
- Rapid heart rate and high BP
- Diarrhoea, loss of appetite
- Flushed, thin and moist skin
- Nails soft and thin
What signs would make you have graves as a leading diagnosis
Goitre with a bruit
What are the investigations for hypothyroidism?
- Free T3 and T4
- TRH/TSH
- Thyroid peroxisomal antibody
What is primary hypothyroidism?
Low levels of thyroid hormones due to destruction of the thyroid gland
What is the treatment of hypothyroidism?
- L thyroxine (T4)
* 75-150mcg per day
Explain the test results in primary hypothyroidism
- Normal/high TSH
* Low T4/T3
What are the test results in secondary hypothyroidism?
- Low TSH
- Low T3/4
- High/normal TRH
If someone presents with hyperthyroidism but is antibody negative what test should you do next?
Thyroid uptake scan
Tests for hyperthyroidism
- TSH
- Free T4
- Total T3
- TSH receptor antibodies
- TPO - thyroid peroxisomal antibody
What are the clinical signs of hyperthyroidism?
- Pretibial myxeoedma
* Thyroid acropachy ( on X ray)
What is the treatment of hyperthyroidism?
- Beta blockers
- Carbimazole
- Radioactive iodine
- Thyroidectomy
What are the complications of thyroidectomy?
- Bleeding
- Scar
- Recurrent laryngeal nerve palsy
What is the aetiology of graves?
- Autoimmune disease
- Genetic susceptibility
- Environmental - iodine, tobacco smoking
- Immune modulating treatment: interferon, alemtuzemab (anti CD52 mAb)
What antibodies are produced in graves?
Activating antibodies directed against the TSH receptor, activating it
What are the antibodies that are produced in Hashimoto’s?
Thyroid peroxisomal antibodies
