Endocrinology Flashcards
1
Q
What is the role of the endocrine system?
A
To maintain a homeostatic environment through hormones
2
Q
How does a hormone work?
A
Post stimulus, the endocrine system will release a hormone into the bloodstream to target cell where they bind to specific receptors for a long term slow response
3
Q
What are the 3 types of signalling?
A
Endocrine - signalling using the circulatory system to receptor elsewhere
Paracrine - signalling to a neighbouring cell
Autocrine - signalling on the signalling cell
4
Q
What are the 3 types of hormones? Where do they bind?
A
Amino Acid Derivative - bind to receptors on plasma membrane
Peptide Hormone - bind to receptor on plasma membrane
Lipid Derivative (steroid / thyroid hormone) - hydrophobic so usually lipid bound, bind to receptor in cytoplasm
5
Q
What endocrine cell secretes glucagon?
A
Alpha Cell on the pancreas
6
Q
Where does glucagon go when secreted from the pancreas?
A
To the liver
7
Q
What type of hormone is glucagon?
A
AA or peptide
8
Q
What is the effect of glucagon binding?
A
It stimulates the liver to breakdown glycogen to secrete glucose into blood to raise blood glucose levels
9
Q
What hormones does the Hypothalamus produce?
A
ADH, oxytocin and regulatory hormones
10
Q
What do the regulatory hormones do?
A
Regulate the hormones of the anterior lobe of the pituitary gland
11
Q
What hormones does the posterior pituitary secrete?
A
Oxytocin and ADH
12
Q
What hormones does the anterior pituitary secrete?
A
Produces and secretes ACTH, TSH, GH, FSH, LH and Prolactin, but only once hypothalamus has secreted regulating hormones to stimulate the release
13
Q
What does the pineal gland secrete?
A
Melatonin
14
Q
What does the thyroid gland secrete?
A
Thyroid hormones - T3 (triiodothyronine), T4 (thyroxine)
Calcitonin
15
Q
What does the parathyroid gland do?
A
Regulates calcium and phosphate
16
Q
What does the thymus secrete
Hint: after atrophy in adults
A
Thymosin
17
Q
What hormone does the heart secrete?
A
Natriuretic peptide
18
Q
What hormones does the digestive tract secrete?
A
Gastrin, somatostatin, secretin, CCK, GIP, VIP
19
Q
What hormones does the pancreas secrete?
A
Insulin and glucagon
20
Q
What hormones does the adrenal cortex release?
A
Cortisol and aldosterone
21
Q
What hormones does the adrenal medulla secrete?
A
Adrenaline and noradrenaline
22
Q
What hormones does the kidney secrete?
A
Erythropoietin and calcitriol
23
Q
What hormone does adipose tissue secrete?
A
Leptin
24
Q
What hormones do the testis secrete?
A
Androgens (testosterone) and Inhibin
25
What hormones do the ovaries release?
Oestrogen, progesterone and inhibin
26
What is the role of ADH?
Targets kidney tubules for water retention (regulation)
27
What is the role of oxytocin?
Human behaviour
| Reproduction (contraction of uterus in childbirth and targets breast for lactation)
28
What is the role of ACTH?
Regulates cortisol
29
What is the role of TSH?
Stimulates thyroid to release hormones
30
What is the role of GH?
Growth
31
What is the role of Prolactin?
Breast development
| Milk production
32
What is the role of FSH?
Regulate the role of the ovaries and testis and gonadotropic regulating behaviour
Growth
Puberty
Reproduction
33
What is the role of LH?
Ovulation
| Formation of corpus luteum
34
What is the role of T3 & T4?
Metabolism
Temperature
HR
35
What is the role of calcitonin?
Regulates calcium and phosphate
36
What is the role of melatonin?
Sleep
37
What is the role of PTH?
Regulation of calcium and phosphate
38
What is the role of thymosin?
T cell production
39
What is the role of natriuretic peptide?
Blood pressure regulation
40
What is the role of gastrin?
Stimulates gastric acid secretion and aids motility
41
What is the role of somatostatin?
Inhibits GH
| Affects neurotransmission / cell proliferation
42
What is the role of secretin?
Regulates water homeostasis
43
What is the role of CCK (cholecystokinin)?
Stimulates digestion of fat and protein
44
What is the role of GIP (gastric inhibitory peptide)?
Stimulates insulin secretion
| Minor role in inhibiting gastric acid secretion
45
What is the role of VIP (vasoactive intestinal peptide)?
Vasodilation
Muscle regulation
Epithelial cell secretion
46
What is the role of insulin?
Lower blood glucose
47
What is the role of glucagon?
Increase blood glucose
48
What is the role of erythropoietin?
Stimulate RBC production in bone marrow
49
What is the role of calcitriol?
Active form of vit D, increases calcium
50
What is the role of cortisol?
```
Stress
can help with blood glucose
metabolism
inflammation
memory
```
51
What is the role of aldosterone?
Sodium reabsorption
| Potassium secretion
52
What is the role of Adrenaline?
Fight or flight
53
What is the role of noradrenaline?
Rest and digest
54
What is the role of leptin?
Fat metabolism
55
What is the role of testosterone?
Male characteristics
| Sperm production
56
What is the role of oestrogen?
Female characteristics
| Egg production
57
What is the role of progesterone?
Menstrual cycle
58
What is the role of inhibin?
Inhibits FSH?
59
What is the role of the thyroid gland?
To produce TH for regulating metabolism
60
Where is the thyroid?
Below the hyoid and larynx, superior to the trachea
61
What is the blood supply for the thyroid?
Superior and inferior a thyroid artery, a branch off the aorta
62
What connects the 2 lobes of the thyroid gland together?
The isthmus
63
What part of the thyroid produces T3and T4?
Follicular cells
64
Explain the mechanism of TRH to increasing TH levels
Stimulus causes hypothalamus to secrete TRH to the anterior pituitary where TSH is released. TSH binds to GPCR on thyroid membrane and activates it, causing GTP to GDP and cause cAMP cascade, increasing TH levels
65
Where is thyroglobulin synthesised? What happens after synthesis?
In the endoplasmic reticulum inside follicles. Golgi apparatus packages it up and into the colloid
66
Why is thyroglobulin important in thyroid function?
It has many tyrosine molecules needed for the synthesis of T3 and T4
67
Explain process of T3 and T4 production
By the aid of Na/I symporters, iodide gets from blood into follicular cell. Iodide then uses pendrine (I/Cl exchange transporter) to get into colloid. Peroxidase oxidises I- to I where it binds to a tyrosine ring (from the thyroglobulin). MIT (monoiodotyrosine) has one iodine attached to tyrosine, DIT (diiodotyrosine) has two iodine molecules attached. MIT&DIT / DIT&DIT can form ester bonds to create T3 or T4.
68
How is T3 and T4 released from thyroglobulin structure?
Pinocytosis packages up the molecules into the follicular cells where lysosomes minds to endosomes with the thyroglobulin and release the tyrosine from the structure. T3 and T4 are released to separate and MIT / DIT molecules can be deionated to release and restart.
69
What type of hormones are T3 and T4?
Lipid hormones - they travel in the blood attached to proteins
70
Which hormone is secreted on higher quantities?
T4 (80%) but T3 is 10x more activated so T4 gets converted to T3 at target cells.
71
What is the action of TH at the cell?
As lipids they can pass through the membranes easily and enter the nucleus where there are 2 receptors - retinoid X receptor, thyroid hormone receptor, which initiate transcription for mRNA response
72
What is the effect of increasing metabolic rate?
Promote growth
CNS development
Metabolism - increased o2 consumption, increased glucose absorption, increased gluconeogenesis, increased glycogenolysis, increased lipolysis, increased protein synthesis and increased BMR.
Cardiovascular -increased cardiac output, increased heart rate, increased respiration
73
What is the blood supply / drainage of the kidneys?
Abdominal aorta supplies the kidneys with blood, the renal veins drain into the inferior vena cava
74
General anatomy surrounding the kidneys
Ureter leaves kidneys and enters bladder to store urine
Adrenal glands sit above the kidney
Liver is superior to the right kidney
Diaphragm sits above the liver and separates the thoracic and abdominal cavities
75
What does erythropoietin do in the kidneys?
During hypoxia,the kidneys produce erythropoietin which stimulates erythropoiesis - production of RBC, increasing O2 carrying capacity
76
What do the kidneys do in response to a decrease in BP?
Produces Renin (enzyme) which converts angiotensinogen (produced by liver) to angiotensin I. This is not very potent so travels to the lungs and ACE converts it into angiotensin II which increases BP.
77
What happens in the kidneys during hypocalcaemia?
Parathyroid releases PTH. Liver produces calcidiol which travels via the blood to the kidneys. PTH stimulates calcidiols conversion to calcitriol (active form of vit D) and it targets:
the intestine - increases calcium and phosphate absorption
the bone - increases bone resorption for increased calcium
kidney nephrons - increases reabsorption of calcium
78
What is another effect of calcitriol on the body
immune system - induces immune cell differentiation
79
Explain the adrenal medulla
It is the centre of the adrenal gland. It is stimulated by sympathetic nerves from the spinal cord to secrete adrenaline and noradrenaline. Increase in these hormones will increase in the fight or flight response in acute stress.
80
Explain the adrenal cortex
The adrenal cortex has three layers:
The glomerulosa - most external, produces mineralcorticoids such as aldosterone
The fasciculata - in the middle, produces glucocorticoids such as cortisol
The reticularis - the most internal, produces androgens
These are responses to long term stresses
81
What is the process for adrenal cortex to release its hormones?
Long term stresses cause the hypothalamus to release corticotropin releasing hormones which target the anterior pituitary releasing ACTH. acth enters circulation and targets the cortex stimulating it release its hormones. Glucocorticoids provide the negative feedback to the hypothalamus.
82
Explain aldosterone action when there is a decrease in BP
A drop in BP causes sodium and water reabsorption, and potassium secretion in exchange which increases blood pressure. Aldosterone secreted from the glomerulosa of the adrenal cortex stimulates the process primarily working in the DCT and CD of nephrons. It also aids in the secretion of the K+.
83
Explain the role of glucocorticoids
Responsible for the negative feedback. It stimulate the liver to make more glycogen stores, gluconeogenesis, protein catabolism, induces insulin resistance and increases fat deposition. This increases glucose until its shunted out if the liver and into the bloodstream and hyperglycaemia
Cortisol also increases blood pressure and suppresses immune system to decrease pain sensation but increases risk of infection. It also increases osteoclasts activity in bone leading to osteopenia and increased risk of osteoporosis. Large role in stress
84
What are androgens effects on the body?
Promote prostate growth and masculine features in men
Important for libido in women, increased androgens means decreased libido.
Minimal link to stress
85
How does ATII respond to a decrease in BP?
Decrease in BP decreases filtration rate and pressure in afferent arterioles of nephrons which stimulates renin release from juxtaglomerular cells to stimulate the RAAS system. ATII is the final product and stimulates the zona glomerulosa to secrete aldosterone to increase BP.
86
What controls the Hypothalamic Pituitary Thyroid Axis?
HPTA is under the control of neurons in the medial region of the paraventricular nucleus of the hypothalamus (PVN) that synthesises and releases TRH into the pituitary portal circulation. Negative feedback of TH control TRH / TSH levels to maintain HPTA. inaccurate levels of TH affect TRH and TSH inversely proportionately
87
How does TSH enter thyroid follicles?
Through the rich capillary blood supply surrounding them
88
What produces calcitonin?
The parafollicular (c) cells
89
What is the diancephalon?
The caudal (posterior) part of the forebrain!containing the epithalamus, thalamus, hypothalamus and ventral thalamus, and the third ventricle
90
Where is GnRH released from?
The hypothalamus
91
What does GnRH do?
The anterior pituitary has blood vessels connecting it and the hypothalamus and the rest of the body. When the hypothalamus releases GnRH it travels in portal blood to AP to stimulate FSH & LH release
92
Where do LH & FSH travel to in men?
The interstitial space surrounding the seminiferous tubules of the testes
93
What cells are in the seminiferous tubules?
Leydig (interstitial) cells
Serotonin (nurse) cells
Spermatogonia (male germ cells) are also found here
94
Explain the production and action of testosterone
LH enters interstitial space and targets leydig cells, causing them to secrete testosterone. Testosterone stimulates sertoli cells and bone and muscle growth, maintains libido, male secondary sex characteristics, accessory glands and organs of male reproductive system. Negative feedback prevents excessive LH release
95
What does FSH do in men?
Targets sertoli cells, stimulating ABP (antigen binding protein) which promotes synthesis of spermatogenesis and spermogenesis. ABP binds to androgens within seminiferous tubules stimulating the sperm production. FSH has negative feedback controlled by inhibin - secreted by sertoli cells
96
Where does LH & FSH travel to in women?
Eggs in the ovaries
97
What is the role of the follicles in the ovaries?
Each month some mature, but only 1 will ovulate to produce an egg. This leaves many primordial follicles and some primary follicles in the ovary with 1 ovulating follicle, starting the menstrual cycle.
98
What are the 2 phases of the menstrual cycle?
Follicular and luteal. Last 14 days each.
99
Explain the changes in hormone concentrations over a month
An increase in GnRH from hypothalamus, causing an increase in LH and FSH.
FSH rises then falls. LH rises and remains steady.
FSH rises during follicular phase as it enters ovaries and stimulates follicle maturation (1° to 2°). Whilst maturing, follicles produce oestrogen which in the first ten days has a negative feedback on the pituitary, inhibiting LH at low concs, hence the steady level (despite GnRH stimulation). FSH is secreted primarily in response to low oestrogen so as it rises, FSH falls, hence the rise and fall.
After 10 days, oestrogen continues to rise but now has a positive feedback and stimulates LH secretion.
100
What hormones does the ovaries produce?
Oestrogen, progesterone & inhibin.
101
What is oestrogen important for?
Stimulating muscle, bone and endometrial growth, maintains female secondary characteristics and glands.
102
What triggers ovulation?
The spike in LH from the change to positive feedback causes the most mature follicle to release the oocyte (egg).
103
What happens after ovulation?
LH, GnRH and FSH will drop. The follicle will develop into corpus luteum (dead follicle). It is now the luteal phase (14 days)
104
What occurs in the luteal phase?
The corpus luteum slowly degrades but also secretes oestrogen, progesterone and inhibin. At the 14th day the oestrogen will fall slightly as the inhibin and progesterone rises.
Don’t need follicle maturation so inhibin has a negative feedback of FSH. Progesterone has negative feedback on GnRH. This also affects LH and FSH, both decreasing.
105
What is the main role of progesterone in women?
Endometrial growth - either to be shed or implanted egg. The degeneration of the corpus luteum allows new follicles to mature and its hormones decrease so progesterone is no longer inhibiting GnRH allowing it to rise again, starting a new cycle.
The now lack of progesterone means endometrial growth is no longer maintained (shedding).
106
What is endometriosis?
The presence of endometrial glands and storms outside the endometrial cavity and uterus musculature
107
What is the anatomy involved in endometriosis?
Vagina, cervix, fallopian tubes, uterus and ovaries
Endometrium is the innermost layer - closest to the uterine cavity, then myometrium and perimetrium
Myometrium has branches of uterine artery called spiral arteries which carry blood, hormones and nutrients into the endometrium
108
What are the clinical signs of endometriosis?
Very bad periods, chronic fatigue, infertility, chronic pelvic pain, severe dysmenorrhea, deep dyspareunia, painful defecation
109
What are the 4 D’s of endometriosis (clinical signs)?
Dysmenorrhea, dyschezia, dysuria, dyspareuria
| Painful periods, poo, pee, sex
110
What are common differential diagnoses for endometriosis?
Adenomyosis
Fibroids
Pelvic inflammatory disease
Ovarian cysts
IBD
IBS
Interstitial cystitis
111
What investigations are done for endometriosis?
Gold standard - Laproscopy
FBC - for infection, anaemia, U&E for kidney function
Abdominal & transabdominal ultrasound
MRI/CT
112
What are the risk factors for endometriosis?
```
Low birth weight
Early menarche
Short menstrual cycles
Late menopause
Red meat
Obesity
Chemical
Genetics
```
113
Protective factors for endometriosis?
Omega 3
Fruit and Veg
Multiple pregnancies
Prolonged lactation
114
What is the basic pathophysiology behind endometriosis?
Pituitary gland releases LH which induces ovulation - initiates egg release from the ovary on day 14. Upon no fertilisation, menstruation will occur in 14 days during which the ovaries are still producing oestrogen and progesterone. By day 28, hormone levels will drop allowing menstruation. In endometriosis, the ectopic tissue will also shed (dysmenorrhea).if it’s in bowel/rectum/genital tract/bladder you’ll also get dyschezia, dyspareuria or dysuria
116
How does the retrograde menstruation theory work?
Endometrial tissue travels back up Fallopian tubes into peritoneal cavity during menstruation
117
How does the vascular and lymphatic dissemination theory work?
Endometrial tissue moves via vasculature or lymphatics elsewhere
118
How does the coelomic metaplasia of multipotent cell theory work?
Ectopic tissue comes from coelomic cells undergoing metaplasia (usually develop into peritoneum / ovary surface cells but instead go to endometrium cells but not present in uterus)
119
How does the impaired immunity theory work?
It’s unknown
120
In terms of pathology, what are the 3 types of endometrial tissue formation?
Ovarian lesion - ovarian cyst formed by ectopic tissue
Superficial peritoneal tissues - on pelvic organ / peritoneum, ‘gunshot’
Deep infiltrative endometrium - solid EM mass >5mm deep under peritoneal surface
121
What is the management of endometriosis?
NSAIDs
Hormonal -
GnRH agonist: stimulates GnRH to stimulate oestrogen & progesterone to maintain endometrium (no periods)
Combined oral contraceptive pill: same as above
Prostagens: same as above
IUD (mirena): releases hormones locally to inhibit periods
Surgical -
Laparoscopic ablation (of ectopic EM tissues)
Open surgery with local resection
Hysterectomy +/- oopherectomy
122
What are the complications of endometriosis?
```
Infertility
Ovarian failure
Development of adhesions
Mental health issues
Autoimmune disease
```
129
What are the 4 theories behind the pathophysiology of endometriosis?
1. Retrograde menstruation
2. Vascular and lymphatic dissemination
3. Coelomic metaplasia of multipotent cell
4. Impaired immunity
