(55) Endocrine investigations Flashcards
What are hormones?
Chemicals secreted by endocrine glands that circulate and influence other tissues producing short and long-term changes in various cells - the cell needs target receptor for that hormone
Describe the basic feedback regulation in endocrine systems
hypothalamus - anterior pituitary - endocrine organ
Where does hypothalamus receive signals from?
- environmental influences
- psychological influences from higher brain
Give 2 examples of what the hypothalamus releases to the pituitary gland? (male)
- FSH releasing factors
- LH releasing factor
Give 2 examples of what the pituitary gland releases in response to hypothalamus signals (male)
- FSH
- LH
Give examples of effects of FSH and LH (from pituitary) on testes (male)
- FSH - sertoli cells, seminiferous tubules, maturation of sperm - inhibin
- LH - leydig cells - testosterone
What effects do inhibin and testosterone have on the regulatory endocrine system? (male)
Negative feedback to hypothalamus and pituitary gland
What provides the negative feedback to the hypothalamus and anterior pituitary in the female?
- estradiol
- progesterone
- inhibin
Describe the basic feedback cycle in terms of thyroid hormones
- anterior pituitary
- TSH
- thyroid gland
- thyroid hormones
- back to anterior pituitary
Describe the basic feedback cycle in terms of parathyroid hormones
- parathyroids
- PTH
- bone, GIT and kidney
- calcium
- back to parathyroids
Describe the basic feedback cycle in terms of insulin
- pancreas
- insulin
- liver, fat, muscle
- glucose
- back to pancreas
Describe the basic feedback cycle in terms of ADH
- hypothalamus
- ADH
- water absorption
- osmolality
- back to hypothalamus
What does decreased TSH and decreased thyroxine indicate?
Pituitary failure
What does increased TSH but decreased thyroxine indicate?
Unresponsive thyroid
What does decreased TSH and increased thyroxine indicate?
Thyroid gland overproduction
What does increased TSH and increased thyroxine indicate?
Pituitary gland overproduction or feedback failure
What is cortisol produced by?
The zona fasciculata of the adrenal cortex within the adrenal gland
When is cortisol released by the adrenal glands?
In response to stress and low blood-glucose concentration
What are the clinical features of Cushing’s disease?
- obesity (moon face, central, shoulders)
- skin (think purple striae, bruising)
- hypertension
- glucose intolerance
- menstrual disturbances/impotence
- thin limbs/muscle weakness
- back pain due to osteoporosis
- psychiatric disturbances (depression, psychoses)
What is the dexamethasone test?
Used to assess adrenal gland function by measuring how cortisol levels change in response to an injection of dexamethasone. It is typically used to diagnose Cushing’s syndrome
What are the causes of Cushing’s syndrome?
- long-term use of corticosteroid medication
- tumour of pituitary gland
- tumour of the adrenal gland
What are the clinical features of adrenal failure?
- tiredness
- weight loss
- pigmentation
- hypoglycaemia
- abdominal pain
- hypovolaemic collapse
Due to adrenal atrophy/destruction
What is a synacthen test?
Tests how well the adrenal glands make cortisol - involves stimulating the adrenal glands and then checking to see if they respond. Synacthen is another name for tetracosactide, the chemical used in the test
Which secretory systems have annual cycle?
Hair growth
