PATHOLOGY- Endocrine disorders Flashcards
Define cell-signalling
Cells communicating in the body to co-ordinate/integrate functions
How are signalling molecules, produced by one cell type, detected by another
Via receptors
Where are the receptors used to detect signalling molecules found
Cell surface
Inter-cellular
What are the 2 purposes of the receptors
Alter gene expression
Alter cell behaviour/function
What 3 mechanisms can signalling occur via
Autocrine
Paracrine
Endocrine
What is autocrine signalling
Signalling molecule acts on the same cell
What is paracrine signalling
Signalling molecule secreted into interstitial fluid, acting on nearby cells
What is endocrine signalling
Signalling molecule secreted into blood stream, acting on distant cells throughout the body
How are body-wide metabolic processes maintained
Via regulatory molecules
What are endocrine glands
Hormone-secreting specialised tissues
What is the endocrine system
System of hormone-secreting specialised tissues
How do hormones travel to target cells distant to site of production
Usually via blood
Explain the general process of the hypothalamic-pituatry axis
- Hypothalamus produces releasing hormones which act on the pituitary gland
- Pituitary gland produces trophic hormones which are released in to the blood stream and can act on specific target glands
- Endocrine glands receives signal from the trophic hormones. It then produces its end product OR acts directly on the cell themselves e.g growth hormone
Most hormones are produced by what
Hypothalamus
What is the pituitary known as
Conductor of endocrine orchestra
What is the pituitary
Where is it
How much does it weigh
What is its role
Small organ
Base of the brain
0.5-1g
Essential control over endocrine system
What are the 2 distinct parts of the pituitary
Anterior pituitary (adenohypophysis, 75-80%)
Posterior pituitary (neurohypophysis)
What is the anterior pituitary (adenohypophysis)
- Stimulated by hypothalamic ‘releasing hormones’
- Releasing hormones pass via “portal” circulation to anterior pituitary
- Secretes six trophic hormones into systemic bloodstream
What is the Posterior pituitary (neurohypophysis)
Neural structures directly from hypothalamus which release 2 trophic hormones, ADH and oxytocin
What is the difference between the anterior and posterior pituitary
In posterior, the signal comes through modified neurons
In anterior, the signal is mediated through the blood stream
What 2 ways is the endocrine system regulated
Hormones (produced in specific circumstances)
Negative feedback
What is negative feedback
Produced hormones ‘feedback’ onto pituitary / hypothalamus to regulate secreting / trophic hormone production, therefore precisely control hormone production
List pituitary dysfunctions
Hyperpituitarism
Hypopituitarism
Local mass effects
What is hyperpituitarism caused by
Excess production of trophic hormones
List examples of where you can see hyperpituitarism
Hyperplasias
Adenomas,
Carcinomas
Secretion of pituitary-like hormones from non-pituitary tumours
Hypothalamus disorders
What is hypopituitarism caused by
Deficient production of trophic hormones
List examples of where hypopituitarism Is present
Ischaemia
Surgery
Radiation
Inflammatory disorders
Mass effect of non-functional pituitary tumours
Post-partum ischaemic necrosis (Sheehan syndrome)
Examples of how local mass effects can case pituitary dysfunction
- Optic nerve (chiasm) - visual field defects
- Raised intra-cranial pressure (^ICP)
- Pituitary apoplexy = haemorrhage causing sudden enlargement = emergency!
What is the most common cause of hyperpituitarism
Pituitary adenomas (most commonly anterior lobe tumours)
What are pituitary adenomas classified by
Cell type
Hormones produced (if functional)
Whe do non-functional tumours tend to present and what size are they
Present later and are usually larger
Why do non functional tumours present later and are usually larger
Functional tumours will be producing abnormal amounts of their trophic hormones so they will be causing some biochemical abnormality, this will give some clinical manifestation when the tumour is much smaller but still producing these chemicals. Whereas nonfunctional tumours have to produce their symptoms by effects of their size
Who do pituitary adenomas usually present in
Most commonly adults, 35-60 years
What do the signs/symptoms of pituitary adenomas depend on
Hormones produced and/ or mass effect
What is the most common pituitary adenoma
Lactotroph pituitary adenoma (30%)
What are lactotroph pituitary adenomas
Prolactin producing tumours
What are lactotroph pituitary adenomas also known as
Prolactinomas
What symptoms does Lactotroph pituitary adenoma cause
Amenorrhea, galactorrhoea, loss of libido, infertility
Is lactotroph pituitary adenoma more easily diagnosed in men or women
Women
What is the second most common pituitary adenoma
Somatotroph pituitary adenoma
What are Somatotroph pituitary adenoma
Growth-hormone producing tumours
what symptoms do somatotroph pituitary adenomas cause
Gigantism in children
Acromegaly in adults
What is corticotroph pituitary tumours
Adrenocorticotrophic hormone (ACTH) producing tumours
What do corticotroph pituitary adenomas cause
Adrenal hypersecretion of cortisol
Hypercortisolism (Cushings syndrome)
What is the thyroid
Where is is located
What level is it on the vertebra
Bi-lobed organ with isthmus
Below, anterior to larynx, close to the trachea
Level of 5th to 7th vertebra
How does the thyroid work
What does this process need to work
- Hypothalamus send a signal via TRH through to the anterior pituitary which acts on the thyrotrophic cells which produces thyrotropin/TSH
- TSH passes into bloodstream and interacts with receptors on thyroid follicular cells/FCs
- This signals thyroid follicular cells to produce the thyroid hormones T3/T4
Iodine
- Thyroid hormones stored by TG in colloid
- When needed and released in to the blood stream by follicular cells, T4 is converted in to T3 (T3 much more active)
- Thyroid hormones binds nuclear thyroid receptor in variety of tissues
- This increases carbohydrate/lipid catabolism
- Also increases protein synthesis which in turn increases basal metabolic rate (BMR)
What is TRH
Thyrotropin releasing hormone
What is thyrotropin also known as
Thyroid stimulating hormone
Where are thyroid hormones such as T3/T4 stored
Stored by thyroid glands in colloid
How are thyroid hormones released from the glands in to the blood stream
Colloid is broken down
List the CLINICAL implications of thyroid disorders and what they are caused by
- Hyperfunction (hyperthyroidism)
- Graves disease, toxic nodules, toxic adenoma
- Hypofunction (hypothyroidism)
- Hashimotos, endemic goitre, iatrogenic (surgery/drugs)
- Structural change (entire gland)
- Graves disease, diffuse / nodular goitre
- Structural change (nodules)
- Dominant nodule in MNG, tumours
List the aetiology of thyroid disorders and what they’re caused by
Autoimmune
* Graves, Hashimotos
- latrogenic
- Surgery, radiation, drugs
- Metabolic
- Endemic goitre, diffuse / nodular goitre
- Neoplastic
- Tumours (adenoma, carcinomas)
Similar aetiologies can cause different what
Clinical features
What are the clinical features of hypothyroidism
Weight gain
Muscle weakness
Constipation
What are the clinical features of hyperthyroidism
Weight loss
Tachycardia
Anxiety
What diseases cause hypothyroidism
Hashimotos thyroiditis
Endemic goitre (I dericiency)
Iatrogenic
What diseases cause hyperthyroidism
Graves disease
Toxic nodules / tumours
What does goitre mean
Enlarged thyroid
What are the effects of euthyroid
Diffuse / nodular hyperplasia (goltre)
Tumours
What is euthyroid
Thyroid levels are normal but structural changes caused
What is Graves’ disease also known as
Diffuse hyperplasia
What is the most common cause of hyperthyroidism
Graves’ disease
What is graves diseases
What does it cause
Autoimmune disorder
Autoantibodies against multiple proteins especially TSH receptor in the thyroid. This activates TSH receptor on thyroid stimulating T3/T4 production. This causes T3/T4 levels to be high with low TSH levels (negative feedback on HPA)
Whta is the most common autoantibody inn Graves’ disease
Thyroid-stimulating immunoglobulin (TS|)
What are the clinical manifestations of Graves’ disease
Symmetrically diffusely enlarged thyroid
Follicles hyperplasticity causing papillary projections
Pale colloid
What are the clinical features of Graves’ disease
- Hyperthyroidism (as above)
- Enlargement of thyroid
- Infiltrative ophthalmopathy (characteristic for Graves)
- Activated T cells cytokines -> fibroblast proliferation, secretion of ECM
- Infiltration of retro-orbital space - protrusion of eyeball (exophthalmos)
How do you diagnose Graves’ disease
High T3/T4, low TSH, autoantibodies
How do you treat Graves’ disease
- Radioactive iodine
- Drugs
- Surgery
What is the most common cause of hypothyroidism
Chronic lymphocytic thyroiditis / Hashimotos
What is Chronic lymphocytic thyroiditis / Hashimotos
What does it cause
Autoimmune disorder
Autoantibodies against thyroglobulin / thyroid peroxidase (diagnostic)
What are the effects of Chronic lymphocytic thyroiditis / Hashimotos
Glands usually enlarged
Lymphocytic infiltration with germinal centre formation
Destruction of thyroid follicular epithelial cells
“Hurthle cell change” - reactive metaplasia due to chronic injury
What are the clinical features of Chronic lymphocytic thyroiditis / Hashimotos
- Hypothyroidism
- † risk of lymphoma / papillary carcinoma
How do you diagnose Chronic lymphocytic thyroiditis / Hashimotos
Low T3/T4, high TSH, TPO autoantibodies