The Adrenal Gland COPY Flashcards
where are the adrenal glands?
Adrenal glands are situated on the superior pole of the kidney in the retroperitoneal space, each weighing ~4g in adults
Similar to the pituitary, the adrenal gland is composed of two quite separate endocrine glands rolled into one structure
what are the 2 seperate parts called?
adnreal medulla (~25%)
adrenal cortex (~75%)
what is the adrenal medulla? and what does it secrete?
a modified sympathetic ganglion (neuroendocrine gland)
Secretes catecholamines from the postganglionic cell, mainly epinephrine (adrenaline) but also norepinephrine and dopamine
amine hormones
what is the adrenal cortex and what does it secrete?
a true endocrine gland and secretes 3 classes of steroid hormones, the first 2 of which are of particular importance:
- Mineralocorticoids e.g. aldosterone: involved in the regulation of Na+ and K+
- Glucocorticoids e.g. cortisol: involved in maintaining plasma glucose
- Sex steroids e.g. testosterone
Aldosterone and cortisol are essential for survival
What is an example of a mineralocorticoid and its function?
Mineralocorticoids e.g. aldosterone: involved in the regulation of Na+ and K+
What is an example of a glucocorticoid and its function?
Glucocorticoids e.g. cortisol: involved in maintaining plasma glucose
Cortex surrounds the _______ and is arranged in _ concentric zones, producing different hormones
medulla
3
Zona glomerulosa =
aldosterone
Zona fasciculata =
glucocorticoids
Zona reticularis =
sex hormones
how does the synthetic pathway in the adrenal cortex work in order to produce different hormones?
All steroid hormones are derived from cholesterol, but different enzymes are found in different adrenal zones, resulting in different end products e.g. enzymes needed to make aldosterone are found only in the zona glomerulosa
Progesterone can be changed into sex steroids, aldosterone and cortisol
Different layers contain different enzymes localising different steroid hormones being localised to the layers
what is the most important enzyme in the synthetic pathway in the adrenal cortex?
what are some defects in 21-hydroxylase?
Defects in 21-hydroxylase is a common cause of congenital adrenal hyperplasia resulting in deficiency of aldosterone and cortisol and associated disruption of salt and glucose balance
Androgen biosynthesis is unaffected so accumulating steroid precursors are channelled into excessive adrenal androgen production
Babies born deficient in glucocorticoids and mineralocorticoids
Babies turn this excess cholesterol into more sex steroids
Babies born with ambiguous genitalia
Struggle to maintain blood glucose balance as loos of glucocorticoids
what is the hypothalamic-pituitary-adrenal pathway?
Also short-loop feedback by ACTH on CRH
A deficit in 21-hydroxylase results in adrenal hyperplasia. Why???
Levels of cortisol decrease resulting in negative feedback loop removing the break on the hypothalamus and anterior pituitary resulting in them giving more production of hormones and they are tropic hormones so cause growth so end up getting hyperplasia of the adrenal cortex
- Lack of 21-hydroxylase inhibits synthesis of cortisol
- This removes the negative feedback on ACTH and CRH release
- Increased ACTH secretion is responsible for enlargement of adrenal glands
- Negative feedback of ACTH on CRH synthesis remains
- Babies become very ill within a few days of birth
Cortisol is a ____________ hormone
glucocorticoid
influences glucose metabolism
~95% of plasma cortisol is…………….
bound to a carrier protein, cortisol binding globulin (CBG)
works with glucagon to increase BG
where are cortisol receptors? and what does binding to the receptor cause?
All nucleated cells have cytoplasmic glucocorticoid receptors
The hormone receptor complex migrates to the nucleus, binding to DNA via a hormone-response element to alter gene expression, transcription and translation