Thyroid dysfunction Flashcards
1
Q
Define goitre.
A
Goitre = enlargement of the thyroid gland
Goitres may be be multi-nodular or consist of a solitary nodule
Nodules may be cystic, colloid, hyperplastic, adenomatous or cancerous
2
Q
What can cause goitre?
A
- Iodine deficiency → most common cause of goitre worldwide
- Autoimmune conditions → Hashimoto’s thyroiditis and Grave’s disease
- Congenital hypothyroidism
- Medication → lithium and amiodarone
- Thyroid cancer
- Benign thyroid neoplasms
- Thyroid hormone insensitivity
3
Q
Describe the pathology of goitre formation.
A
- Thyroid cell growth and function are mainly stimulates by TSH via the TSH receptor
- TSH activity is mediatedthrough the alpha subunit of stimulating G portein
- Signals from cell surface receptors are sensed by G proteins and transducer to cAMP
- Increased cAMP levels cause growth and excess function of thyrocytes
4
Q
Describe the role of isotope scanning in the investigation of thyroid lesions.
A
- able to distinguish functioning toxic nodules and thyroid metastases from follicular and papillary carcinomas is best with iodine uptake studies
- low iodine uptake in a single palpable nodule gives a risk of malignancy fo 10-25%, falling to 1-3% if multiple nodules are demonstrated on the scan
5
Q
Describe the role of fine needle aspiration in the investigation of thyroid lesions.
A
- should be performed in any thyroid nodule >1cm and in <1cm if there is any clinical or US suspicion of malignancy
- results of FNAC are very sensitive differential diagnosis of benign and malignant nodules
6
Q
Describe the role of USS in the investigation of thyroid lesions.
A
- extremely sensitive for thyroid nodules and is used as a 1st line diagnostic procedure for detecting and characterising nodular thyroid disease
- USS features associated with malignancy:
(i) hypoechogenicity
(ii) microcalcification
(iii) absence of peripheral halo
(iv) irregular borders
(v) solid aspect
(vi) intranodular blood flow and shape - assess the status of lymph node chains
7
Q
List the possible causes of thyroid enlargement in a euthyroid patient.
A
- Intrathyroidal hyperplastic/neoplastic:
- thyroid adenomas
- non-toxic multinoduular goitre (as a result of multiple colloid nodules/hyperplastic nodules/thyroif adenomas) - Intrathyroidal neoplastic (malignant):
- papillary, medullary, follicular, anaplastic thyroid tumours - Congenital/developmental/anatomical:
- thyroid cysts
- thyroglossal duct cysts - Infectious/inflammatory/autoimmune:
- acute suppurative thyroiditis (usually bacterial infection)
- subacute granulomatous thyroiditis (de Quervain’s thyroiditis)
- painless lymphocytic thyroiditis (initial hyperthyroid stage, followed by subsequent hyperthyroidism and then return to euthyroid state)
8
Q
Describe the features of a benign thyroid adenoma and how it may present.
A
- Features:
- can be inactive or active (called a toxic adenoma in this case)
- will typically grow up to 3cm before symptoms develop, can grow as large as 10cm
- typically a solitary, spherical and encapsulated lesion
- almost all thyroid adenomas are follicular adenomas - Presentation:
- may be asymptomatic, with the mass as the only feature
- if active, patient will present with features of hyperthyroidism (heat intolerance, weight loss, agitation/anxiety, tachycardia etc.)
9
Q
Describe the clinical features of papillary thyroid carcinomas.
A
- most common form of thyroid cancers (~70%)
- usually presents between 35-40 y/o and is 3 times more common in women
- usually presents when <1cm in size
- excellent long-term prognosis
- can spread locally to compress the trachea and recurrent laryngeal nerve
- can metastasise (usually to lung and bone)
10
Q
Describe the clinical features of follicular thyroid carcinomas.
A
- second most common form of thyroid cancers (~10%)
- tends to occur in areas of low iodine
- 3 times more common in women, tends to present between 30-60 y/o
- greater propensity to metastasise to lung and bones than PTC
11
Q
Describe the clinical features of medullary thyroid carcinomas.
A
- arises from the parafollicular calcitonin-producing C cells
- accounts for ~5-8% of all thyroid malignancies
- malignant C cells produce and secrete large amounts of CEA and calcitonin
- familial MTC arises as part of MEN2a/2b
12
Q
Describe the clinical features of anaplastic thyroid carcinomas.
A
- most aggressive thyroid tumour
- arises from the follicular cells of the thyroid but does not retain any of the biological features of the original cells
- <2% of thyroid tumours, most commonly occurring between 60-70 y/o
- will usually develop form a pre-existing well-differentiated thyroid tumour
- ~50% of patients present with metastases (most lung, but also liver, bones + brain)
- mean overall survival <6 months regardless of treatment
13
Q
Describe the treatment options for papillary thyroid cancer.
A
- Surgery:
- total thyroidectomy is most commonly performed
- can perform unilateral total lobectomy for low-risk patients (<1cm) - 131-I treatment:
- ablation of remnant thyroid tissue if tumour >4cm or in tumours <4cm with high-risk features - External beam radiotherapy:
- may be considered after complete resection and 131-I therapy if tumour is still large/ extracapsular spread/poor prognostic features
- can be used in palliative care - Targeted therapies:
- small molecule tyrosine kinase inhibitors (vandetanib, sorafenib, sunitinib)
14
Q
Describe the treatment options for follicular thyroid cancer.
A
- Surgery:
- total thyroidectomy is most commonly performed
- can perform unilateral total lobectomy for low-risk patients (<1cm) - 131-I treatment:
- ablation of remnant thyroid tissue if tumour >4cm or in tumours <4cm with high-risk features - External beam radiotherapy:
- may be considered after complete resection and 131-I therapy if tumour is still large/ extracapsular spread/poor prognostic features
- can be used in palliative care - Targeted therapies:
- small molecule tyrosine kinase inhibitors (vandetanib, sorafenib, sunitinib)
15
Q
Describe the treatment options for medullary thyroid cancer.
A
- Surgery:
- all patients should have a total thyroidectomy
- only potentially curative intervention
- + central and ipsilateral neck node disseciton - External beam radiotherapy:
- post-op for macroscopic remnant to maximise local control
- may cause inoperable tumour to become operable - Chemotherapy:
- doxorubicin first line
