Topic 8 - Endocrinology Flashcards
What are the main endocrine glands?
- Hypothalamus/Pituitary
- Thyroid
- Parathyroid
- Pancreas
- Adrenal
- Ovaries/Testicles
What is the pituitary gland?
-Controls most glands in the body
What are the two lobes of the pituitary gland?
- Anterior pituitary
- Posterior pituitary
What does the anterior pituitary gland do?
Produces various hormones
What does the posterior pituitary gland do?
Stores various hormones
Which hormones does the anterior pituitary produce?
- Growth hormone (GH)
- Adrenocorticotrophic hormone (ACTH)
- Gonadotrophins (FSH and LH)
- Thyroid stimulating hormone or thyrotrophin (TSH)
- Prolactin (PRL)
What does the Growth hormone do?
Used for skeletal growth.
What is ACTH used for?
Stimulating the adrenals to produce steroids.
What do gonadotrophins do?
Stimulate the ovaries and testes to produce sex hormones
What does TSH do?
Stimulates the thyroid to produce thyroid hormones
What does prolactin do?
Stimulates breast milk production
Which hormones does the posterior pituitary gland store?
- Antidiuretic hormone (ADH)
- Oxytocin
What does ADH do?
Stimulates water reabsorption in the kidneys
What does oxytocin do?
Helps uterine contractions during labour
How is the pituitary gland controlled?
By the hypothalamus
What stimulates ACTH secretion?
Corticotrophin releasing hormone (CRH)
What stimulates GH secretion?
Growth hormone releasing hormone (GHRH)
What stimulates TSH secretion?
Thyrotropin releasing hormone (TRH)
What stimulates FSH and LH secretion?
Gonadotrophin releasing hormone (GnRH)
Prolactin is inhibited by what?
The hypothalamus
Which hormone switches off ACTH and CRH?
Cortisol
What hormone switches off GH and GHRH?
Growth hormone
Which hormones switch off TSH and TRH?
Thyroid hormones
Which hormones switch off FSH, LH and GnRH?
Sex hormones
Which glands are controlled by the pituitary?
- Adrenals (steroids)
- Thyroid
- Ovary/testicle
Which glands are not controlled by the pituitary?
- Adrenal medulla
- Parathyroid
- Pancreas
- Gut Hormones
What do the adrenal medulla produce?
Adrenaline and Noradrenaline
What does the parathyroid do?
Control calcium levels
What does the pancreas do?
Control sugar levels
What are the components of the thyroid gland?
- Midline isthmus (just below cricoid cartilage)
- Right lobe
- Left lobe
What are the structural specificities of the thyroid gland?
- Thyroid cells are arranged in follicles and produce thyroid hormones
- Contains C cells which produce calcitonin
- Thyroid hormones regulate gene expression and aspects of organ function
How is calcium metabolism controlled?
- 4 Parathyroid glands (located behind the thyroid)
- Kidneys (Excrete calcium and produce active vitamin D)
- Gut (Absorbs calcium)
What are the components of the adrenal glands?
- Adrenal cortex
- Adrenal medulla
What does the Adrenal cortex produce?
- Cortocosteroids (cortisol)
- Androgens (male hormones)
- Mineralocorticoid (Aldosterone)
What does the Adrenal medulla produce?
-Catecholamines (adrenaline, noradrenaline and dopamine)
What controls blood pressure?
The renin-angiostensin system
Which hormone stimulates secretion of adrenaline?
Pituitary hormone ACTH
Where can aldosterone be produced?
Adrenal medulla
Lack of which hormone can be lethal?
Cortisol
Which cells produce testosterone?
Interstitial or Leydig
Which cells produce sperm?
Germ cells in the seminiferous tubules
Which cells produce inhibin in the testes?
Sertoli cells (also help in sperm production)
What tests are used to detect hormonal abnormalities?
- Static tests
- Stimulation tests
- Suppression tests
What is the static test for primary hypothyroidism?
-Thyroid hormones T3 and T4
-TSH
(positive = T3 and/or T4 elevated, suppressed TSH)
When is a stimulation test used?
For suspected hormonal under-secretion where a static test isn’t enough
When is a suppression test used?
For some hormonal over-secretion
What are some examples of stimulation tests?
- ACTH test for adrenal insufficiency
- Glucagon stimulation
- Insulin stress test for pituitary failure
What are some examples of suppression tests?
- Giving steroids and testing for endogenous steroid production
- Giving glucose and testing for GH secretion (glucose switches it off in normal individuals)
What are the types of diseases of the endocrine glands?
- Over-secretion (benign tumours)
- Under-secretion (gland destruction_
- Tumours/nodules (with normal hormone production)
What can gland destruction be attributed to?
- Inflammation (eg. autoimmune)
- Infarction
- Other
How does prolactin over-secretion present?
- Galactorrhoea
- Amenorrhoea in women
- Sexual dysfunction in men
- Headaches and visual field problems in large tumours
What usually causes prolactin over-secretion?
A pituitary tumour secreting prolactin (prolactinoma)
How is a prolactinoma diagnosed?
-Static test
if inconclusive:
-Pituitary MRI
What may cause mildly raised prolactin levels?
- Sexual intercourse
- Nipple stimulation
- Stress
- Large number of drugs (antidepressants/antipsychotics)
- Non-functioning pituitary tumour
How can prolactinomas be treated?
Medically - doesn’t usually require surgical intervention
What does GH excess cause in children?
- Excessive growth spurt and increased size of feet and hands
- If left untreated: gigantism
What does GH excess cause in adults?
- Acromegalic face
- Wide and large hands/feet
- Increased sweating
How is GH excess diagnosed?
- Suppression tests
- Glucose is given followed by GH measurement
- Imagining is necessary to confirm presence of a pituitary tumour
How is a GH excreting pituitary tumour treated?
- Surgical removal of the tumour
- Radiotherapy and medical therapy may be needed to remove remnants
What can cause Cushing’s syndrome?
- Pituitary secreting ACTH tumour (Cushing’s disease)
- Adrenal tumours secreting cortisol
- Cancers producing ACTH (eg. lung cancer)
How does Cushing’s present?
- Growth arrest in children
- Face: Round, acne, hirsuitism
- Fat distribution: truncal obesity, thin extremities
- Skin abnormalities: Thin, easy to bruise, striae on abdomen
- Complications: Hypertension, diabetes mellitus, high infection risk, poor wound healing
How is Cushing’s diagnosed?
- Suppression tests
- Dexamethasone suppression test to suppress endogenous cortisol production
How is Cushing’s treated?
Pituitary and adrenal: -Surgery -Radiotherapy/medical treatment in pituitary Cancer related: -Treating original cancer
What can cause thyroid hormone overproduction?
- Primary hyperthyroidism
- Secondary hyperthyroidism (pituitary TSH secretion)
What can cause hyperthyroidism?
- Graves disease (80%)
- Toxic nodule or toxic MNG (15%)
- Thyroiditis (1%)
- Drug induced
- Rarities
Which drug can cause hyperthyroidism?
Amiodarone
How does hyperthyroidism present?
- Hyperactivity
- Irritability
- Insomnia
- Heat intolerance/Increased sweating
- Palpitations
- Weight loss despite overeating
- Menstrual problems
What would you examine for in suspected hyperthyroidism?
- Thyrotoxicosis: Hand tremor, Increased sweating, Fast pulse
- Inspection of thyroid gland: Smooth (Graves’ disease), Nodular (toxic nodules), Tender (thyroid inflammation)
- Thyroid eye disease: Swelling around eyes, Protrusion of the eyeball, Paralysis of eye muscles
How is hyperthyroidism tested for?
Static tests!
- Raised thyroid hormone
- Suppressed TSH
How is hyperthyroidism treated?
- Anti-thyroid drugs (disease remission in 50% patients after 6-18 months, but can rarely suppress WBC production)
- Radioactive iodine (destroys thyroid gland)
- Surgery
How does GH deficiency present in children?
Failure of growth
How does GH deficiency present in adults?
- Nothing
- Tiredness
- Depression
How is GH deficiency tested for?
Stimulation tests
- Glucagon stimulation test
- Insulin stress test (lowers blood glucose to force more GH secretion)
How is GH deficiency treated?
GH replacement injections
What causes steroid under-secretion?
- Adrenal failure
- Pituitary failure
How does steroid under-secretion present?
- Failure to grown in children
- Severe tiredness
- Dizziness due to low blood pressure
- Abdominal pain, vomiting and diarrhoea
How is steroid under-secretion tested for?
Stimulation tests
- Synacthen test (giving ACTH) if primary adrenal failure suspected
- GST or IST if secondary adrenal failure suspected
How is steroid under-secretion tested?
-Replacing the missing hormone (tablets)
Failure to diagnose may result in death. If this is suspected, Cortisol should be given even before the investigation results are back.
What is primary hypothyroidism?
Thyroid failure and inability to produce thyroid hormones.
- Usually autoimmune
- Can be drug induced
What is secondary hypothyroidism?
Failure to produce TSH
-Usually part of complete pituitary failure
What are the symptoms of severe hypothyroidism?
- Weakness and dry skin
- Sensations of cold and decreased sweating
- Impaired memory
- Constipation
- Weight gain
- Hair loss
How is hypothyroidism diagnosed?
-Static test of thyroid function
How is hypothyroidism treated?
Thyroid hormone replacement (tablets)
What causes sex hormone deficiency?
- Primary: ovarian or testicular failure
- Secondary: pituitary failure
How does sex hormone deficiency present in males?
- Erectile dysfunction
- Reduced libido
How does sex hormone deficiency present in females?
-Menstrual abnormalities (amenorrhoea)
What can cause amenorrhoea?
- Uterine problems
- Ovarian problems
- Pituitary problems
- Hypothalamic problem
How is sex hormone deficiency diagnosed?
Static tests
- Testosterone in males
- Oestradiol in females
- FSH/LH
How is sex hormone deficiency treated?
- Hormone replacement therapy
- Pituitary hormone replacement
What are the causes of pituitary failure?
-Large tumour
-Infarction
-Other
(multiple hormones affected, static and stimulatory tests for diagnosis)
How would pituitary hormone deficiency be tested for?
Endocrine tests:
-Basal tests: thyroid function, E2, Prolactin
-Dynamic tests: Glucagon stimulation, Insulin stress test
MRI imaging
What can cause increased parathyroid hormone production? (pituitary independent)
- Primary hyperparathyroidism
- Cancers
- Drugs
- Other
What does hypercalcaemia cause?
- Thirst and passing too much urine
- Constipation
- Abdominal pain
