Physiology Of The Thyroid Gland Flashcards
Give four functions of thyroid hormone
Growth
Metabolism
Normal brain function in adults
Myelation of fibres
What is the 1st endocrine gland to develop in embryo
Thyroid gland
Describe the structure of the thyroid gland
Made up of two lobes, the left and right lobes and an isthmus in the middle, lies over the trachea.
Two functions of thyroid gland
Production of thyroid hormones
Organification of Iodine
Name three types of thyroid hormones, and the differences with each other.
- Thyroxine ( tetraiodothyronine) - T4
- Has 4 iodine molecules per hormone, is the most abundant form of thyroid hormone in plasma. - Tri-iodothyronine- T3
- Has 3 iodine molecules per hormone, is the most active/ potent form of the thyroid hormones. - (Thyro) calcitonin- concerned with calcium metabolism.
Explain the process of organification of iodine(3)
- Follicular cells synthesise the thyroglobulin and enzymes of the colloid.
- The sodium iodine symporter brings iodine inside the cells. The pendrin transporter transports iodine into the colloid.
- Enzymes in the colloid add iodine to tyrosine creating T3 and T4.
- Thyroglobulin leaves the colloid in a vesicle.
- Intracellular enzymes separate T4 and T3 from the protein.
- Free T3 and T4 enter circulation.
Name the enzyme responsible for the organification of iodine
Thyroperoxidase
What affect the release of thyroid hormones(1)
Tonic release
Clinical features of congenital hypothyroidism
Prolonged jaundice
Goitre
Failure to gain weight
Dry skin, hair
What are the symptoms of hypothyroidism (3)
Dry skin
Hair loss
Weight gain with poor appetite
Feeling cold
Constipation
Poor concentration and memory
What are the signs of hypothyroidism (4)
Dry skin
Puffy face
Bradycardia
Carpal tunnel syndrome
What are the primary causes of hypothyroidism (3)
Autoimmune hypothyroidism (eg. Hashimoto’s thyroiditis)
Iatrogenic
Drugs
Infiltrative disorders
Congenital
Iodine deficiency
What are the secondary causes of hypothyroidism
Hypopituitarism
Hypothalamic diseases
What are the symptoms of hyperthyroidism (3)
Heat intolerance and sweating
Weight loss with increased appetite
Diarrhoea
Polyuria
Palpitations
Loss of libido
What are the signs of hyperthyroidism (2)
Tachycardia
Tremour
Goitre
Warm, moist skin