hormones Flashcards
list 4 hormones produced by the hypothalamus
gonadotrophin releasing hormone
corticotrophin releasing hormone
growth hormone releasing hormone
thyrotrophin releasing hormone
list 6 hormones produced by the anterior pituitary gland
growth hormone prolactin adrenocorticotrophin releasing hormone (ACTH) thyroid stimulating hormone (TSH) luteinising hormone follicle stimulating hormone
list 2 hormones released by the posterior pituitary gland
oxytocin antidiuretic hormone (ADH)
list the 3 layers of the adrenal cortex and state which hormones are released
list the hormones released by the adrenal medulla
adrenal cortex:
zona glomerulosa-mineralocorticoids e.g. aldosterone
zona fasciculata-glucocorticoids e.g. cortisol
zona reticularis-gonadocorticoids e.g. androstenedione and DHEA
adrenal medulla-catecholamines- adrenaline and noradrenaline
3 classifications of hormones based on chemical structre
amino acid based e.g. catecholamines, thyroid hormones, ACTH, ADH, TSH, insulin, glucagon, growth hormone
steroid based e.g. gonadal hormones, adrenal hormones
eicosanoids e.g. prostaglandin
what is a hormone?
a diverse collection of chemical messengers which travel through the blood and bind to specific cellular receptors at target tissues
Describe how amino acid based hormones differ to steroid hormones in terms of their (i) solubility in water and (i) ability to cross target cell membranes
AA based hormones are water soluble and are therefore unable to pass through the phospholipid bi-layer of the cell membrane at target tissues *except thyroid hormone
Steroid based hormones are lipid soluble and are therefore able to cross through the phospholipid bi-layer of the cell membrane at target tissues
4 general actions of hormones
- alteration of cell membrane permeability or excitability e.g. noradrenaline acting on the SA node
- stimulation of synthetic activity or secretion e.g. enzymes, proteins; LH acting on Leydig cells causing the production of testosterone
- activation/deactivation of enzymes e.g. cortisol on intracellular enzymes
- stimulation of mitosis e.g. growth hormone causing growth
Explain the difference (at the cellular level) between a second messenger system and direct gene activation
Which class of hormones act as second messengers?
Second messenger system: act upon receptors embedded in cell membrane of target cells; rely on intracellular signalling (second messengers) to mediate their effects
Direct gene activation: bind to receptors within the cytosol because the hormone can diffuse through the cell membrane
Amino acid based hormones EXCEPT thyroid hormone (T3 and T4) use second messengers
Provide some examples of molecules that are used as second messengers
Cyclic AMP e.g. ACTH, FSH, LH, Glucagon, PTH, Calcitonin
Tyrosine Kinase e.g. insulin
3 main types of hormonal stimuli
humeral
neural
hormonal
explain the stimulus for release and action of:
oxytocin
antidiuretic hormone
oxytocin-
stimulated by cervical/uterine stretching/suckling of infant on breast
uterine contractions (labour) and milk ejection
andidiuretic hormone-
stimulated by increased blood osmolarity or decreased blood volume
increases the reabsorption of water by inserting aquaporins in the DCT and CD on the kidney nephron
all hormones released by the anterior pituitary gland, except … act by using Cyclic AMP second messenger systems
growth hormone
in cases of anterior pituitary hypersecretion, which two hormones are most often produced in excess?
growth hormone and prolactin
explain the stimulus for release and function of:
growth hormone
prolactin
growth hormone-
stimulated by GHRH due to low GH levels/ low blood sugar, fatty acids and high levels blood AA
anabolic hormone that stimulates somatic growth
mobilises fats for use as energy source
prolactin-
stimulated by low dopamine levels, enhanced by breast feeding and oestrogens
promotes mammary gland development and milk production
sexual gratification after orgasm
explain the stimulus for release and function of:
adrenocorticotrophic hormone
thyroid stimulating hormone
ACTH-
stimulated by Corticotrophin Releasing Hormone in response to stress
promotes release of hormones from adrenal cortex
cleavage product is alpha-melanocyte stimulating hormone which produces Melanin for skin pigmentation
TSH-
stimulated by Thyrotropin Releasing Hormone (TRH)
stimulates thyroid gland to release thyroid hormone T3 and T4
explain the stimulus for release and function of:
Folicle Stimulating Hormone
Luteinising Hormone
FSH-
stimulated by GnRH
F: Stimulates maturation of ovarian follicle and production of oetrogens
M: Stimulates production of androgen-binding protein by sustentacular cells
LH-
stimulated by GnRH
F: Triggers ovulation and converts the ruptured follicle into the corpus luteum (the corpus luteum secretes progesterone and some oestrogen)
M: Stimulates production of testosterone by interstitial (Leydig) cells
what is the vascular supply of the adrenal glands?
superior, middle and inferior adrenal arteries
differentiate Cushing’s Disease from Cushing’s Syndrome
Cushing’s Disease- hypercortisolism due to increased ACTH secretion from the anterior pituitary; most common cause is pituitary microadenoma.
Cushing’s syndrome= hypercortisolism has occurred independently of pituitary ACTH secretion; most common cause is iatrogenic-glucocorticoid hormone therapy.
summarise the clinical features of hypercortisolism
Effects on metabolism:
o Truncal obesity, development of striae
o Lemon on toothpicks appearance vs. generalised obesity
o Moon face with flushed red cheeks, buffalo hump
o Muscle weakness/wasting, myalgia, arthralgia
o Osteoporosis, pathological #
o Hyperglycaemia=insulin resistance
Effects on blood pressure= hypertension
Effects on immunity= poor wound healing, skin infections
Involvement of Zona Reticularis may cause features of hyperandrogenism: hirsutism, menstrual irregularity
what is another name given to primary adrenocortical insufficiency?
Addison’s Disease
differentiate between primary and secondary adrenocortical insufficiency
Primary Adrenocortical Insufficiency:
• Due to intrinsic dysfunction of adrenal cortex
• Also referred to as Addison’s Disease
• Associated with increased ACTH levels but decreased cortisol
Secondary Adrenocortical Insufficiency:
• Causes include: Pituitary or hypothalamic dysfunction
• May also occur after glucocorticoid therapy
• Associated with decreased ACTH and decreased cortisol levels
what is the most common cause of Addison’s Disease?
autoiimune attack
other causes: infection, metastatic spread, bilateral adrenalectomy
Define the term phaeochromocytoma
list some clinical features
A tumour arising from the chromaffin cells of the adrenal medulla; most common cause of excess catecholamine production
HTN or complication HTN e.g. AMI, stroke, heart failure, AAA
intermittent catecholamine secretion e.g. pallor, sweating, tremours, anxiety, abdo pain, weight loss etc.
