Basic Principles Flashcards
At what stage in pregnancy is a goitre seen
Perinatal period
Many endocrine disorders are associated with defects in what
GPCRs
What do GPCRs act as
Biological sensors
What is a good example of intrinsic tyrosine kinase activity
Insulin receptor
What are 2 examples of cytokine receptors
Prolactin receptor and growth hormone
What are cytokine receptors linked to
Tyrosine kinase activity
Steroid hormones are typically intracellular or extracellular
Intracellular
Where exactly are steroid hormone receptors located
either in the cytoplasm or the nucleus
What are included in the nuclear receptor family
Oestrogen, androgen receptos
What do steroid/receptor complexes do ?
Bind DNA response elements
When do receptors translocate to the nucleus
Only when a hormone or a ligand is present
Give an example of a steroid hormone receptor and what it does
Testosterone
It causes alterations in gene transcriptions with interactions with DNA
What can a circulating corticosteroid that is bound to by either a hormone or a ligand cause
Transactivation or transrepression
What is the master regulator of hormones
Pituitary gland
At what sites can the pathways be disrupted
Hypothalamus
Pituitary gland
Peripheral glands e.g. thyroid, adrenal, cortex or gonad
What does a disruption in a pathway result in
Endocrine problems
Where is the site of central regulation from the hypothalamus
Anterior pituitary gland
What are the 5 hormones secreted by the anterior pituitary gland
Growth hormone LH/ FSH Adrenocorticotropic hormone Thyroid stimulating hormone Prolactin (PRL)
What is secreted by the posterior pituitary gland
ADH or vasopressin
What factors affect the ability to accurately measure hormone levels
Pattern of secretion The presence of carrier proteins Interfering agents Stability of hormone (consider 1/2 life) Absolute concentrations
What is a major determinant of hormone concentration?
Rate of secretion
Measuring hormones is typically determined by highly refined by what
Feedback loops - ie. need to know the right time to measure the right hormone levels (circadian rhythm)
What types of hormones are commonly evaluated
Thyroid hormones
Steroid hormone production (e.g. cortisol)
Growth hormone evaluation
Reproductive and sex hormone (e.g. testosterone)
Prolactin
Calcium and parathyroid homrone
Why might reproductive hormones be evaluated
Infertility
Puberty
Loss of libido
Erectile dysfunction
What is the function of renin and aldosterone and what gland are the associated with
Adrenal gland
They regulate salt and water balance
When might TSH not be a reliable marker of Thyroid status
If the patient had a primary hypothalamic pituitary problem e.g. a tumour and was therefore unable to secrete TSH
What does the thyroid axis rely on
highly regulated feedback control
What does the patient have if they have a raised TSH
Hypothyroid
What does the patient have if they have a suppressed TSH
Hyperthyroid
What hormone has the strongest circadian rhythm in humans
Cortisol
When are the cortisol levels highest
First thing in the morning
When should cortisol be measured
First thing in the morning when they should be at their peak
Describe the release of growth hormone from the pituitary
Under pulsatile release from and short lived in the blood
What happens if there is excess growth hormone before puberty was complete
Marked elongation within the long bones of the body
What happens if the growth hormone was in too little quantities around puberty
Dwarfism
Describe the relationship between gamete production and sex hormone synthesis
These are coordinated so there is a close relationship
What is prolactin secreted by
Lactotroph cells of the anterior pituitary
The effects of Prolactin are mediated by what
The prolactin receptor (PRLR)
Where is thirst tightly regulated within
The hypothalamus
What are the 3 main steroid hormones that can lead to specific endocrine disorders
Aldosterone
Cortisol
Testosterone
What happens if the body can’t produce the precursors of steroid hormones
There will be an excess of the hormone
When is biochemical testing typically perfumed with regards to imaging
Before imaging
To test for hormone excess, what test do we do
Suppression test
To test for hormone deficiency, what test do we do
Stimulation test
In what situation might there be a need for combined imaging/ biochemical testing
Adrenal vein sampling or petrosal sinus sampling
If there is a cortisol deficiency, what does this mean
You have adrenal insufficiency
If there is primary adrenal failure, what disease is this known as
Addison’s disease
Cortisol excess is more commonly known as what
Cushing’s syndrome
Stimulation test with cortisol is known as what
Synacthen tes
What is the cortisol suppression test known as
Dexamethasone suppression test
What are some symptoms of Cushing’s syndrome
Cushingoid facies Acne Hirsutism Abdominal striae and centripetal obesity Inter scapular and supraclavicular fat pads proximal myopathy osteoporosis hypertension impaired glucose tolerance
What is important to know before removing any adnreal gland
Whether it is unilateral or bilateral
What are some causes of Cushing’s syndrome
High levels of ACTH
Increased production of cortisol
Ectopic ACTH
Exogenous steroids (causing ACTH to be switched on)
Investigation for Cushings can be done as an outpatient or always an inpatient
Outpatient
If there is a failure to suppress in a low dose dexamethasone suppression test what does this indicate
Cushing’s syndrome
If the ACTH is low, what does this indicate
Adrenal origin is likely
What can be lost if there is a pituitary tumour or an adrenal tumour
The circadian rhythm
What is MEN
Multiple endocrine neoplasia
What gene is affected in MEN1
MEN 1 gene - 11q
What gene is affected in MEN2
RET gene - 10q
What are 2 of the most important things to try and avoid with patients with MEN1
Premature morbidity and mortality
