Thyroid pathology Flashcards
What are the three embryological abnormalities of the thyroid gland?
Lingual thyroid gland
Thyroglossal duct cyst
Retrosternal thyroid gland
How is the thyroid gland arranged histologically?
Follicles containing thyroglobulin and lined by follicular epithelium
Scattered C cells/parafollicular cells
What do C cells secrete?
Calcitonin
What does calcitonin do?
Reduces blood calcium levels (minimally relevant)
Which thyroid-related hormone is secreted from the hypothalamus to act on the anterior pituitary?
Thyrotropin releasing hormone
Which thyroid-related hormone is secreted from the anterior pituitary to act on the thyroid?
Thyroid stimulating hormone
Which hormones are secreted from the thyroid in response to hormonal stimulation from the pituitary?
Triodothyronin (T3)
Thyroxine (T4)
Which specific cells of the thyroid does thyroid stimulating hormone act on?
Thyroid follicular epithelium
Which receptor does thyroid stimulating hormone bind to? Where is this receptor found?
TSH receptor on follicular epithelium
Which type of receptor is TSH receptor?
G-protein coupled receptor
How do G-protein coupled receptors work?
Convert GTP to GDP to produced cAMP which increases the production of thyroid hormones
T3 and T4 only circulate when bound to plasma proteins. T/F
False - they exist in bound or free forms
How do T3/4 work on target tissues?
Bind to target cells >
Bound T3/4-receptor complex translocates to the cell nucleus >
Binding to thyroid response elements on target genes >
Gene transcription and increase in BMR
When might the thyroid gland atropy?
When its function is reduced
Enlarged thyroid glands are capable of causing breathing and/or swallowing difficulties. T/F
True - if thyroid glands enlarge enough they can cause local mass effects
Define the terms thyrotoxicosis and hyperthyroid
Thyrotoxicosis - too much thyroid hormone
Hyperthyroid - hyper function of the thyroid tissues
Is there a genetic component to autoimmune thyroid disease?
Yes
What autoimmune condition is associated with autoimmune thyroid disease?
Vitiligo
What is the most common cause of hyperthyroidism?
Grave’s disease
What is a pituitary cause of thyrotoxicosis?
TSH secreting pituitary adenoma
Name a cause of ectopic thyrotoxicosis
Struma ovarii
Grave’s disease is autoimmune. T/F
True
Is graves disease more common in woman or men?
Woman
What age group typically presents with Grave’s disease?
20-40 y/o
What are the antibodies against in Grave’s disease?
Thyroid stimulating hormone receptor
Thyroglobulin
Thyroid peroxisomes
Name an anti TSH receptor antibody involved in Grave’s
Thyroid stimulating immunoglobulin
What is the triad of features found in Grave’s disease?
Hyperthyroidism with diffuse goitre
Exopthalamos (TED)
Pretibial myxoedema
Why do you get thryoid eye disease in Grave’s?
Fibroblasts within the eye and surrounding tissues express TSH receptors
What is the most common cause of hypothyroidism?
Hashimoto’s thyroiditis
Is hashimoto’s thyroiditis autoimmune?
Yes
Who typically gets Hashimoto’s thyroiditis?
Middle aged woman
Is Hashimoto’s thyroiditis associated with other autoimmune conditions? Is it associated with HLA?
Yes & yes
What are secondary and tertiary causes of hypothyroidism?
Pituitary tumour
Hypothalamic tumour
What are other causes of hypothyroidism?
Iodine deficiency
Lithium medication
Iatrogenic (hyperthyroidism treatment)
Is hashimoto’s thyroiditis more common in woman or men?
Women
What is the typical age range who gets hashimoto’s thyroiditis?
45-60 y/o
Does hashimoto’s thyroiditis have a genetic component?
Yes