Thyroid Gland Flashcards
Describe the structure of the thyroid gland
2
Composed of two lateral lobes joined by the isthmus and may have a third lobe (the pyramidal lobe which extends upwards from the isthmus)
Divided into follicles
How many lobes are there in the thyroid gland?
Three
What is the third lobe of the thyroid gland called?
The pyramidal lobe
What are the two lateral lobes of the thyroid gland joined by?
Isthmus
What is the thyroid gland divided into?
Follicles
What is produced by follicle cells?
Thyroxine (T4) and Triiodothyronine (T3)
What is T4?
Thyroxine
What is T3?
Triiodothyronine
What cells produce calcitonin?
Parafollicle cells
What is produced by parafollicle cells?
Calcitonin
Where is thyroid stimulating hormone released?
From the pituitary gland in the brain
What is the role of thyroid stimulating hormone?
Stimulates the synthesis and secretion of thyroid gland hormones
What are the three main roles of the thyroid?
Regulation of metabolism and energy balance
Regulation of growth and development
Regulation of the activity of the nervous system
What are the three main signs of thyroxine deficiency in fetal development?
Fewer and smaller neurons
Defective myelination
Mental retardation
What are the three main signs of thyroxine deficiency in early years of life?
Low stature
Poor development of the brain
Poor development of the reproductive structure
What is the name of the disorder which is caused by thyroxine deficiency in early life?
Creatinism
How does thyroxine deficiency cause creatinism?
Creatinism results from low levels of iodine
Low levels of iodine result from a lack of thyroxine as without it iodine can not be utilised by the thyroid
What is the name of the disorder which is caused by thyroxine deficiency in adult years?
Myxedema
What is the name of the disorder which is caused by hypersecretion of thyroxine ?
Grave’s Disease
List two of the most common symptoms of Grave’s Disease
Enlarged thyroid (called goitre)
Oedema behind eyes (called exophthalmos)
What is the role of calcitonin?
Regulates the homeostasis of blood calcium and phosphate
How does calcitonin lower calcium and phosphate in the blood?
By inhibiting bone breakdown and accelerating bone uptake of these minerals
What controls calcitonin levels?
They are controlled directly by blood calcium feedback on the secretary cells
