Endocrine pathology Flashcards
Where does the pituitary gland sit?
- in the sella turcica
- of the sphenoid bone
- attached to the hypothalamus
- composed of two parts which are embryologically and functionally distinct
What hormones does the anterior pituitary secrete?
FLAG TP
- Follicle stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Adrenocroticotrophic hormone (ACTH)
- Growth hormone (GH)
- Thyroid stimulating hormone (TSH)
- Prolactin
The secretion of all six anterior pit hormones is in turn regulated by hormones from the hypothalamus, which reach the pituitary through a portal system of blood vessels
What are the posterior pituitary hormones?
- Antidiuretic hormone
- Oxytocin
Both are synthesised in the hypothalamus and then pass down nerve fibres in the pituitary stalk to be secreted by the posterior pituitary.
What is the most common disease of the anterior pituitary?
- pituitary adenomas
- tumours derived from glandular tissue of ant pit
- most cases are sporadic but may occur as part of the MEN-1 syndrome
What are the 2 main ways that pituitary adenomsa can cause clinical effects?
- Mass effects
- Endocrine effects
What are the mass effects?
- bitemporal hemianopia (bc tumour causes compression of optic chiasm + thus affects optic nerves)
- diplopia (tumour causes compression of cranial nerves III, IV or VI)
- non-specific symptoms related to any intracranial mass eg. headache
What is the difference between a functional and non-functional adenoma?
With pit adenomas, you get mass effects and then you get endocrine effects too:
- functional adenomas - produce symptoms related to XS hormone secretion (most commonly prolactin, GH, ACTH), bc of this, functional tumours are v small at presentation
- non-functional adenomas - do not produce hormones, often larger at presentation bc they present via mass effects rather than endocrine dysfunction. Many non-functional adenomas remain tiny and never come to clinical attention bc they do not cause mass effects.
What is a common type of functional pituitary adenoma?
- prolactinoma
- produce excess prolactin
- presentation depends on patient’s age + sex
How do prolactinomas present in women of reproductive age?
commonly present with either:
- oligomenorrhoea (infrequent or v light menstruation - 4-9 periods/year)
- or galactorrhoea (spontaneous flow of milk from breast unassociated w/ pregnancy or breast feeding)
These patients often have very small tumours and so present early
How do prolactinomas present in men and post-menopausal women?
- usually present with mass effects such as headache or visual disturbance
- may present with symptoms such as galactorrhoea
- the tumours are typically larger at presentation
How do GH-secreting pituitary adenomas present?
- acromegaly
- rare clinical syndrome resulting from XS secretion of GH
Why does acromegaly result from XS GH?
somatic and metabolic effects of chronic GH hypersecretion are predominantly mediated by high levels of insulin like growth factor-1 (IGF-1), which is secreted by the liver in response to GH stimulating it.
IGF-1 then has a growth effect on tissues.
What are the specific tissue effects of IGF-1, in acromegaly - ie. what is the presentation?
- Acromegalic facies (big nose, prognathia, course features)
- Headaches + thickend calvaria
- Left ventricular hypertrophy
- Hypertension
- Insulin resistance
- Hepatomegaly
- Impotence + loss of libido
- Amenorrhoea in women
- Large hands + thickened skin
- Hyperostosis
- Degenerative joint disease
- Peripheral neuropathy
- Large feet + heel pad
Acromegaly is a serious condition in which there is a doubling in mortality compared with normal populations, why is this?
- mainly due to high incidence of cardiovascular disease due to left ventricular hypertrophy and hypertension
- acromegaly is a diabetogenic state (ie. it causes insulin resistance), which is a strong risk factor for cadiovascular disease
What are the commonest causes of thyrotoxicosis?
- Graves’ disease (80%)
- toxic multinodular goitre (a nodule within a multinodular goitre whcih autonomously secreted thyroid hormones independently of TSH)
- a functional thyroid adenoma (a follicular adenoma producing thyroid hormones)
- other: drugs (amiodarone) + certain types of thyroiditis
Are TSH-secreting pituitary adenomas a common cause of thyrotoxicosis?
very rare cause of thyrotoxicosis
Where are the adrenal glands located?
- in the retroperitoneum
- superior to the kidneys
What are the 2 functional parts of the adrenal gland?
- cortex
- medulla
What is the function of the adrenal cortex?
composed of (from outermost to innermost) + produce:
- zona glomerulosa -> mineralocorticoids (aldosterone)
- zona fasciculata -> glucocorticoids (cortisol)
- zona reticularis -> androgens
What is the function of the adrenal medulla?
Produce catecholamines such as adrenaline and noradrenaline
What is the HPA axis?
- hypothalamus secretes CRH
- stimulates anterior pituitary to secrete ACTH
- this acts on adrenal cortex to stimulate release of cortisol
- cortisol has a -ve feedback effect on hypothalamus + ant pit, so suppresses the secretion of CRH and ACTH respectively
What syndrome do ACTH-secreting adenomas present as?
Cushing’s syndrome (see later cards for more detail)
What are causes of Cushing’s syndrome?
- exogenous admin of glucocorticoids
- pituitary adenoma secreting ACTH
- adrenal cortical adenoma
- paraneoplastic syndrome
Cushing’s syndrome is due to persistent XS circulating glucocorticoids (cortisol). What are common presenting symptoms and signs?
- Weight gain (trunkal obesity, moon face, buffalo hump)
- Mood change (lethargy, depression, irritability)
- Proximal myopathy
- Gonadal dysfunction (ED, irregular menses, hirsuitism)
- Acne
- Hypertension, DM, osteoporosis
- Petechiae, striae, poor healing + bruising
- Peripheral neuropathy
- Bitemporal hemianopia
