Hypo and Hyperthyroidism Flashcards
What is hyperthyroidism
Due to excess T3 and T4
Is hyperthyroidism usually caused by excess TSH
No, this is very rare
What is the most common cause of hyperthyroidism
Graves’ disease
What is thyrotoxicosis
Clinical syndrome resulting from the effect on the tissues due to circulating T3 and T4 - increased metabolic rate
What three diseases usually result in hyperthyroidism
- Graves’ thyroiditis
- Functioning adenoma
- Toxic nodular goitre
What is strums ovarii
A rare tumour in which thyroid hormones are produced and released into the blood - leading to an excess
Signs of Graves’ thyroiditis
- Associated with diffuse goitre
- Thyroid is enlarged, firm and red
- Hyperplasia of acing epithelium
- Reduction in colloid
- Accumulation of lymphocytes in lymphoid follicle formation
Why does the thyroid appear red in Graves’ thyroiditis
Due to increased vascularisation
How does Graves’ thyroiditis occur
IgG are produced (autoimmune) which bind to thyroid epithelial cells and stimulates it like TSH would - stimulatory hypersensitivity
What are the IgG autoantibodies known as
LATS - Long-acting thyroid hypersensitivity
Symptoms of individuals with Graves’ thyroiditis
- Exopthalmos (bulging of eyes due to deposition of fat in retrobulbal area + inflammatio/oedema of extra-ocular muscles) - MOST COMMON
- Accumulation of mucopolysaccharides in dermis
- Finger clubbing
Do adipocytes have receptors to TSH
Yes
What is nodular goitre
Thyroid enlarges (usually due to iodine deficiency)
How does hypothyroidism effect the metabolic rate
Lowers it
Symptoms of hypothyroidism
- Accumulation of mucopolysaccharides in the face - myxoedema face
How does hypothyroidism effect a newborn
- Physical growth and mental development impaired - Cretinism
Where is cretinism common
Areas where diet contains insufficient iodine for thyroid hormone synthesis
What is the most common cause of hypothyroidism
Hashimoto’s thyroiditis
Describe some iatrogenic causes of hypothyroidism
- Removal of the thyroid surgically
2. Certain drugs causing it as a side-effect
What is myxoedema
swelling of the skin and underlying tissues giving a waxy consistency
What can happen to the thyroid later on in patients with hypothyroidism
Atrophy and fibrosis
Appearance of the thyroid during hypothyroidism
- Firm, fleshy and pale
- Densley infiltrated by plasma cells and lymphocytes with lymphocytic colloid formation
- reduction in colloids
- Thyroid epithelial cells enlarge and develop eosinophilic granular cytoplasm
Why do thyroid epithelial cells develop eosinophilic granular cytoplasms in hypothyroidism and what are they now known as
Due to proliferation of mitochondria
Askanazy cells
Why is there a transient phase at the beginning of Hashimoto’s thyroiditis
- Damage to the thyroid follicles lead to release of thyroglobulin into circulation
What would appear in blood tests for patient’s who are positive for Hashimoto’s thyroiditis
- Two autoantibodies
One reacting with thyroid peroxidase
One reacting with thyroglobulin
Where are the autoantibodies in Hashimoto’s thyroiditis formed
Locally by plasma cells infiltrating the thyroid
Define goitre
Enlargemnt of the whole gland WITHOUT hyperthyroidism
What is parenchyma’s goitre
- First hyperplasia of the thyroid epithelium
- Loss of coloids
- Eventually less active areas are compressed by hyperplastic areas
- Fibrosis may separate the less active areas - multi nodular goitre
How can multi-nodular goitre be detected
They can be palpated clinically
What is colloid goitre
- No epithelia hyperplasia (unlike parenchyma)
- Lots of colloid found
- Colloids form cysts
- Haemorrhage found
Symptoms of colloid goitre
- Tracheal compression (difficulty breathing)
2. Stridor
What is stridor
Harsh or greeting sound during breathing
How is hypothyroidism caused (3 ways)
- Iodine deficiency
- Inherited enzyme defects in T3 n T4 synthesis
- Drugs that induce hypothyroidism
Under a histological slide, what is an indication of colloid goitre
The follicles are distended by accumulated colloid
How do we deal with people who come into a clinic with a solitary mass in the thyroid (this is very common)
- Checking thyroid secretory status (serum TSH, T3 and T4 levels)
- Ultrasound imaging and checking for thyroid neoplasia \
What two ways do solitary masses tend to go
- Turn out to be one large nodule in a multi nodular goitre
2. May be neoplastic (rare)
What is the most common thyroid tumour
Follicular adenoma
Signs of follicular adenoma
1, Solid mass within a fibrous capsule, compressing the adjacent gland
2. Centre shows haemorrhage and cystic changes
Histological signs of follicular adenoma
- Compact follicles lined by epithelium
- Nuclear hyperchromatism
- Very little colloid
- Fibrous capsule not breached by tumour
- Epithelial cells have large central clear areas in nuclei
How common is a follicular carcinoma
Rare
Why is a follicular carcinoma rare
Because tumours are well-differentiated
What is follicular carcinoma associated with
Exposure to ration (x-rays)
In what aged patients is papillary adenocarcinoma found
Less than 45s
Appearance of a papillary adenocarcinoma
- Non-encapsulated infiltrative mass
- Firm - due to fibrosis
- White - due to fibrosis
What do papillary adenocarcinomas look like histologically
- Epithelial papillary projections between which calcified capsules (psammoma bodies) are present
- Nulcei have clear central areas
How do papillary adenocarcinomas metastasise
Via the lymphatic within the thyroid glands and the cervical lymph nodes
Why does papillary adenocarcinoma have a good prognosis
As it is a slow-growing tumour
Follicular adenocarcinoma vs follicular adenoma
- Adenocarcinoma shows blood vessels and invasion of capsule
How does follicular adenocarcinoma metastasise
Blood stream to the bones and lungs
Why does follicular adenocarcinoma have a good prognosis
Retains ability to take up 131-I
Where are anapaestic carcinomas common
Elderly
Why does anapalastic carcinomas have a poor prognosis
Because it results in rapid local invasion of structures such as the trachea
What causes medullary carcinoma
Thyroid C-cells
What do C-cells produce
Calcitonin
Role of calcitonin
Lowers Ca levels in the blood:
- Inhibits osteoclast activity in bones
- Inhibits renal tubular absorption of Ca and phosphate
What acts antagonistically to calcitonin
Vitamin D and PTH
How does non-hodgkin’s lymphoma relate to thyroid
Originates in the thyroid in Hashimoto’s thyroiditis more commonly
Where do lymphomas of the thyroid gland originate from
Neoplasms of mucosa-associated lymphoid tissue
