Endocrinology Flashcards
What are the main endocrine glands
Hypothalamus Pituitary Thyroid Parathyroid Pancreas Adrenal Ovaries/testicles
What is the pituitary gland and what are its two lobes
Controls most glands in the body
Found in the brain just below the hypothalamus
Anterior produces various hormones
Posterior stores various hormones
What hormones are produced by the anterior lobe of the pituitary
Growth hormone: for skeletal growth
ACTH: stimulate adrenals to produce steroids
Gonadotophins (FSH and LH): stimulate the testicles and ovaries to produce sex hormones
Thyroid stimulating hormone (TSH): stimulates the thyroid to produce thyroid hormones
Prolactin (PRL): stimulates breast milk production
What hormones are stored in the posterior lobe of the pituitary gland
Antidiuretic hormone (ADH): stimulates water reabsorption by the kidneys Oxytocin: helps uterine contractions during labour
What hormones are released by the hypothalamus
Corticotrophin releasing hormone (CRH) which stimulate ACTH secretion
Growth hormone releasing hormone (GHRH) which stimulates GH secretion
Thyrotrophin releasing hormone (TRH) which stimulates TSH secretion
Gonadotrophin releasing hormone (GnRH) stimulates FSH and LH secretion
How is prolactin secretion controlled
It is under an inhibitory effect of the hypothalamus
How are pituitary hormones switched off
Negative feedback which acts on pituitary and hypothalamus
What glands and hormones are not controlled by the pituitary
Adrenal medulla: produce adrenaline and noradrenaline
Parathyroid: controls calcium levels
Pancreas: controls sugar levels
Gut hormones
What is the thyroid composed of
Midline isthmus( just below the cricoid cartilage)
Right lobe
Left lobe
What are the characteristics of thyroid hormones and cells
Thyroid cells are arranged in follicles and produce thyroid hormones
Thyroid contains C cells which produce calcitonin
Thyroid hormones interact with their receptors in various organs, regulating gene expression and aspects of organ function
T3 is active and T4 is inactive
What organs are involved in calcium metabolism and how
Parathyroid: main glands controlling calcium metabolism
Kidneys: calcium excretion and production of active vitamin D
Gut: Absorption of calcium
Bone: storage of calcium
Thyroid: produce calcitonin
What are the two parts of the adrenal gland
CONTROLLED BY PITUITARY: Adrenal cortex: Corticosteroids (cortisol), Androgens (male hormones)
Mineralocorticoid (aldosterone) consolle by renin angiotensin system
NOT CONTROLLED BY PITUITARY (related to blood pressure):Adrenal medulla: Catecholamines (adrenaline, noradrenaline and dopamine)
What are the characteristics of the ovaries
Situated in the pelvis on either side of the uterus
Contain follicles containing oocyte at different stages of maturation
Stimulated first half of cycle by more FSH, second half of cycle by more LH
Secrete Inhibin (negative feedback), oesradiol (1st half) ,progesteron (2nd half)
What is testicular maldescent
When the testicles remain in the pelvis and don’t descend into the scrotum
What are the testicles composed of
Interstital/leydig cells: produce testosterone
Seminiferous tubules: made up of germ cells producing sperm
Sertoli cells: help in sperm production and produce inhibin
FSH controls sperm production
LH controls testosterone production
What are types of abnormalities within the glands
Hormonal over secretion
Hormonal under-secretion
Primary: problem with gland itself
Secondary problem with gland controlling the gland itself
Tumour/nodules int the gland without affecting hormone secretion
What are static tests
One blood test and immediately diagnosis hormonal over or under secretion
How is primary hyperthyroidism diagnosed in static test
Elevated T3 and/or T4
Suppressed TSH
What is a stimulation test
For suspected hormonal under-secretion where static test is not enough
Is individual fails to respond to a stimulation test then gland failure is diagnosed
What are examples of stimulation tests
Synacthen test
Glucagon stimulation
Insulin stress test
What are suppression tests used for
Some hormonal over-secretion
What are examples of suppression tests
Giving steroids and testing for endogenous steroid production (healthy person this would be switched off)
Giving glucose and testing GH secretion (glucose switches of GH secretion in normal individuals)
What tens to cause over and under secretion
Over-secretion: benign tumours
Under-secretion:gland destruction due to: inflammation, infarction, other
Both can be caused by tumours/nodules with normal hormone production
What is prolactin over-secretion
Due to prolactin secreting tumour
Increased breast milk production (galactorrhea)
Amenorrhea (irregular periods)
Sexual dysfunction in men
Headaches and visual field problems in large tumours
Diagnosed by static test
What can cause mildly raised prolactin
Sexual intercourse
Nipple stimulation
Stress
Large number of drugs including antipsychotics and antidepressants
Non-functioning pituitary tumour, compressing the hypothalamus and interfering with the inhibitory effect on prolactin secretion
What is the result of growth hormone over-secretion
In child: excessive growth spurt and increased size of feet and hands; if left untreated leads to gigantism
In adult: affects the skin, soft tissue and skeleton; acromegalic face; wide and large hands/ feet; increased sweating
What causes Cushing’s syndrome
Pituitary secreting ACTH tumour (Cushing’s disease)
Adrenal tumours secreting cortisol
Cancers producing ACTH (such as lung cancers)
How does Cushing’s present
Growth arrest in children
Face: Round, Acne, Hirsuitism
Fat redistribution: truncal obesity, thin extremities
Skin abnormalities: thin skin, easy bruising, striae on abdomen
Complications: hypertension, diabetes, high risk of infection, poor wound healing
What are the causes of hyperthyroidism
Graves’ disease: Genetic autoimmune condition, 80%
Toxic nodule or toxic multi-nodule-goitre, 15%
Thyroiditis, 1%
Drug induced: amiodarone
Rarities
How do people with hyperthyroidism present
Hyperactivity Irritability Insomnia Heat intolerance and increased sweating Palpitations Weight loss despite overeating Menstrual problems Can have thyroid eye disease (swelling, paralysis, proptosis) if Graves' disease
How do you examine hyperthyroidism
Hand tremor Increased sweating Fast pulse Inspection of thyroid: Enlarged: Smooth: Graves' disease Nodular: toxic nodule Tender: thyroiditis
What is the treatment for hyperthyroidism
Anti-thyroid drugs:
Disease remission in 50% of patients after treatment for 6-18months, can rarely suppress white cell production
Radioactive iodine: destroys the thyroid gland
Surgery
What are the characteristics of growth hormone deficiency
Children: failure to grow
Adults: no symptoms, tiredness, depression
How is growth hormone treated
Injections of growth hormone replacement, very expensive
How do patients with steroid under-secretion present
Failure to grow in children Severe tiredness Dizziness due to low blood pressure Abdominal pain Vomiting in diarrhoea
What are the symptoms of hypothyroidism
Weakness and dry skin Sensation of cold and decreased sweating Impaired memory Constipation Weight gain Hair loss
What causes pituitary failure
Large tumour
Infarction
Something else
How to test for pituitary failure
Test biochemically -> Static tests -> dynamic tests -> image pituitary last
How do steroid and thyroid hormones alter the cellular activity
Act within the nucleus to alter gene transcription, switching genes on and off
Binding of hormones to proteins and the binding of the receptor-hormone complex (a transcription factor) to specific DNA sequences
What is the clinical relevance of nuclear hormone receptors
They are drug targets
What do steroid hormones derive from
Cholesterol
What do thyroid hormones derive from and where are they synthesised
Tyrosine in the thyroid gland
