Endo: Thyroid Disease Flashcards
True/false: Thyroid develops embryologically from laryngeal epithelium
False, develops from pharyngeal epithelium and descends in neck
Why does ectopic thyroid tissue occur?
Thyroid descends down neck as it develops
Weight of thyroid
15-20g
Thyroid receives nerve supply from ____ _____ nerves
cervical sympathetic
Influences thyroid secretion by acting on blood vessels
Thyroid follicles are surrounded by___ epithelium
The centre of the follicle contains ____ which stores the thyroid hormone
Thyroid follicular epithelium
Colloid
- ___ released by pituitary after action of THRH from hypothalamus
- TSH acts on thyroid to release __ and lesser amounts of ___
- TSH
2. T4, lesser amounts of T3
T3 and T4 are reversibly and loosely bound in circulation to ________
Thyroxine binding globulin TBG
Maintains level of free T3 and T4 within narrow limits
What is a multinodular goitre?
NON NEOPLASTIC, common disorder, presents later in life
Progressive cycle of hyperplasia followed by degeneration and fibrosis. Gland becomes enlarged and nodular
Multinodular goitre: A degenerate process of ______ and regression.
Hyperplasia
Histology: Cystic change within follicles so they are dilated and filled with colloid. Surrounded by fibrosis. Gland shows architectural nodularity and is overall enlarged
Multinodular goitre
Most common causes of hyperthyroidism? (3)
Diffuse toxic hyperplasia (Graves) (85%)
Toxic multinodular goitre
Toxic adenoma
Uncommon causes of hyperthyroidism
Thyroiditis
Exogenous thyroxine or TSH
Secreting pituitary adenoma
Neonatal thyrotoxicosis
Cardiac and MSK clinical features of hyperthyroidism
Overactivity of SNS
Tachycardia
Palps.
Arrhythmia
Congestive HF
Atrophy of MSK tissues
OSTEOPOROSIS
Neuromuscular clinical features of hyperthyroidism
Tremor
Hyperactivity
Anxiety
Irritability
Skin and GI clinical features of hyperthyroidism
Warm skin
Sweating
Increased appetite
Weight loss
Increased bowel mobility
How is hyperthryoidism diagnosed?
Free levels of T4 in peripheral blood
TSH level will be suppressed
Radioactive iodine uptake will be increased
Causes of hypothyroidism
Radiation/surgery
HASHIMOTO THYROIDITIS
Idiopathic primary hypothyroidism (blockade of TSH receptors)
Iodine deficiency
Drugs (lithium, iodides)
Pituitary or hypothalamus lesions lowering TSH or TRH
Hypothyroidism in infancy:
___ in iodine deficient areas.
Poor development of ____ and ___ along with mental retardation
Endemic
Skeleton, CNS
Another name for hypothyroidism
Myxoedema
Clinical features of adult hypothyroidism (myxoedema)
Decreased sweating Constipation Weight gain Feeling cold Accumulation of matrix substances in subcut. tissue
Slowing of physical/mental activity
Depression
LOW CARDIAC OUTPUT-SOB, decreased exercise tolerance
Diagnosis of hypothyroidism
Difficult clinically
Decreased T3, T4
Raised TSH
**NB pituitary or hypothalamic causes may have low TSH
Reidel’s thyroiditis
Progressive fibrous replacement of the thyroid tissue
Causes hypothyroidism
Palpation thyroiditis
Histological changes due to pre-operative handling or palpation of tissue
Hypothyroidism
Gross changes seen in Hashimotos thyroiditis
Symmetrical atrophy of thyroid tissue
Hypothyroidism
Hashimotos thyroiditis: Histology features are ____ tissue and epithelial ___ cell change (oncocytic cells)
Lymphoid
Pink
Histology:
The thyroid epithelial cells also show a characteristic change. They have abundant eosinophilic, or pink cytoplasm, and this is known as oncocytic, or Hurthle cell metaplasia.
Hashimoto’s thyroiditis
What is most common cause of thryoiditis?
Hashimoto’s thyroiditis
Pathology of Hashimoto’s thyroiditis
Autoimmune disease due to defect in T cells (cellular and humoural immunity)
Activation of thyroid specific CD4 cells and CD8 cytotoxic cells
B cells secrete anti TSH factors
HYPOTHYROIDISM
High prevalence of HLA DR3 and DR5 in which thyroid disease?
Hashimoto’s thyroiditis
Who gets Hashimoto’s thyroiditis?
F:M is 15:1
Typically 45-65
Presentation of Hashimoto’s thyroiditis?
Painless thyroid enlargement
What diseases are linked to Hashimoto’s thyroiditis?
Increased incidence of B cell lymphoma of thyroid
Associated with other auto-immune diseases
What are the specific manifestations of Grave’s disease?
Infiltrative opthalmopathy: Immune mediated infiltration of periocular muscles and soft tissue
Pretibial myxoedema
Age range affected by Grave’s disease?
20-40 years
Mostly females
HLA B8 and DR3 linked to which thyroid disease
Grave’s
Pathology of Grave’s disease
TSH receptor autoantibodies mimic TSH and stimulate thyroid hormone production
Lab findings in Grave’s disease
Raised free T3 and T4, TSH decreased
Histology: Diffuse tightly packed hyperplastic follicles with pseudopapillae. Involves both lobes. No nuclear features
Grave’s
What percentage of cancers are made up of malignant thyroid cancers?
1%
Populations most affected by thyroid cancer
Younger adults
Females more than men
Features suggestive of thyroid cancer (3)
Solitary nodule
Enlarged nodes
Nodule in YOUNGER PT
Thyroid adenoma: Discrete solitary mass derived from ____ epithelium
Follicular
Thyroid adenoma: Shares architectural features with follicular cancer except has an intact surrounding ____-
capsule
Which type of thyroid mass has these histological subtypes? Microfollicular
Macrofollicular
Oncocytic (Hurthle cell)
Thryoid adenoma
True/false: There is no vascular invasion associated with a follicular adenoma
True
Risk factors for thyroid malignancy
NB: Most cases are sporadic
Ionising radiation
Genetic factors (eg Cowden syndrome, FAP, familial PTC syndrome)
MEN syndrome- medullary carcinoma
Which thyroid cancer is linked to MEN syndrome?
Medullary carcinoma
Multiple endocrine neoplasia syndrome
4 subtypes of thyroid carcinoma?
Papillary (80%)
Follicular (10%)
Medullary(5%)
Anaplastic(<5%)
Most common subtype of thyroid cancer?
Papillary carcinoma
Age range affected by papillary carcinoma
20-40 years
Papillary carcinoma metastases %?
10-15%
10 year survival rate of papillary carcinoma
98%
Mechanism of follicular carcinoma metastasis?
Blood-borne route
Mechanism of papillary carcinoma metastasis?
Via lymph nodes
Difference between follicular carcinoma and adenoma?
Carcinoma breaches the capsule and/OR invades the BVs
Medullary carcinoma: _____ carcinoma derived from parafollicular __ Cells- sheets, nests or trabeculae of small dark cells
Neuroendocrine
C Cells
Which hormone is secreted by medullary tumours that can aid diagnosis?
Calcitonin
Stromal change associated with medullary carcinoma?
Pink amyloid deposition
What percentage of medullary carcinomas are inherited?
Up to 25%
Associated with MEN 2A and 2B
and familial MTC (medullary thyroid carc.) syndrome
5 year survival rate of medullary carcinoma
80% but may metastasis early
Which main thyroid cancer subtype is undifferentiated?
Anaplastic carcinoma (pleomorphic or spindled tumour cells)
Mortality of anaplastic carcinoma?
90-100%!!!
How does anaplastic carcinoma spread?
Rapid extensive local infiltration of the neck
What is a poorly differentiated carcinoma?
Tumour which is intermediate morphologically between a differentiated thyroid tumour and an undifferentiated one (anaplastic)
True follicles or well formed papillae are not the main feature of these tumours
5 year survival of poorly differentiated carcinoma
50%
Thyroid lymphoma: May complicate _____.
Usually ___ cell and low grade
Thyroiditis
B
