Thyroid Gland Pathology Flashcards
What are the two types of endocrine cells in the thyroid gland? (2)
- Follicular cells (endoderm origin), surround protein-rich lakes of pink colloid
- C-cells (neural crest origin)
What are thyroid follicular cells?

What are the roles of the thyroid hormones (triiodothyronine, T3 and thyroxine, T4)? (4)
TSH tells thyroid follicular cells to increase the synthesis and secretion of thyroid hormones

Physiology of the synthesis of thyroid hormones (5)

What are thyroid C cells? (3)

What is calcitonin? (3)
- Hypocalcemia, thyroid C cells accumulate secretory granules.
- Hypercalcemia, thyroid C cells will release these granules.
- Opposes the effects of parathyroid hormone (PTH).
- C cells secrete calcitonin in response to hypercalcaemia
- Long term hypercalcaemia results in hyperplasia of C cells

Species variation in the shape of the thyroid gland (2)
- Cows = big, butterfly-shaped
- Cats = two little slugs on lateral surfaces of trachea
What are the developmental malformations of the thyroid gland? (2)
- Ectopic thyroid tissue
- Thyroglossal duct cysts



What is ectopic thyroid tissue? (4)

What are thyroglossal duct cysts? (5)
- Epithelium resembling thyroid follicles (if near the larynx)
- Usually less than 1 cm diameter
- Can rupture – inflammation
- Rarely undergo malignant transformation
- DDx for abscesses around the head and neck

What causes hypofunction of the thyroid gland? (2)
- Lymphocytic (immune-mediated) thyroiditis (inflammation)
- Idiopathic follicular atrophy




What is lymphocytic thyroiditis? (4)

What is idiopathic follicular atrophy (4)
- Treatment (thyroid hormone replacement) exacerbates atrophy – negative feedback reduces TSH
- Few, small, follicles and fat infiltration

What are the features of hypothyroidism? (4)
- Hypercholesterolaemia -> atherosclerosis
- Myxedema
- Sparse wool or hair
- Subnormal growth rate




What are the features of hypothyroidism? (4)
- Hypercholestrolaemia -> athersclerosis
- Myxedema
- Sparse wool or hair
- Subnormal growth rate
What is a goitre? (4)

What causes follicular hyperplasia? (4)
- Iron deficiency
- Iodine excess
- Goitrogens - substances that cause goitres
- Congenital defects in synthesis of thyroid hormone
What is a diffuse goitre?
Typically compensatory, TSH-induced response to hypothroidism
What is a multinodular gotire? (3)
- Hyperplastic follicular cells acting autonomously (independent of TSH) to cause hyperthyroidism e.g. in old cats
- Groups of delinquent thyroid follicular epithelium ignore the hypothalamus & pituitary gland
- Rest of thyroid gland undergoes atrophy (negative feedback resulting in low TSH)




















