T1 L3, Pituitary gland Flashcards
What type of circulation does the pituitary gland have?
Sinusoidal circulation (containing pores that allow free flow of proteins)
Which gland sits right below the optic chiasm?
The pituitary gland
Which structure is the pituitary gland directly attached to?
The hypothalamus. They’re connected by the stalk
What are some functions of the Hypothalamus?
- Integrates functions that maintain chemical and temperature homeostasis
- Functions with the limbic system
- Controls the release of hormones from the anterior and posterior pituitary gland
Which Hypothalamic releasing hormones stimulates secretion of FSH and LH?
Gonadatropin releasing hormone (GnRH)
Which Hypothalamic releasing hormone inhibits growth hormone secretion?
Somatostatin (SS)
Which Hypothalamic releasing hormones inhibits prolactin secretion?
Dopamine
Which Hypothalamic releasing hormone stimulates secretion of ACTH?
Corticotropin releasing factor (CRF)
What is ACTH?
Adrenocorticotropic hormone which controls the production of cortisol
Which Hypothalamic releasing hormone stimulates secretion of TSH?
Thyrotropin releasing hormone (TRH)
Which Hypothalamic releasing hormones stimulates secretion of GH?
Growth hormone releasing hormone (GHRH)
What is GH?
Growth hormone. It fuels childhood growth and helps maintain tissues and organs throughout life
How are hormones from the hypothalamus delivered to the anterior pituitary gland?
Through the hypothalamic-hypophyseal portal system
How does prolactin act as a natural contraceptive?
It stops ovulation
What is the role of oxytocin in breastfeeding?
It’s responsible for transporting milk into the ducts which connect to the nipple
It contracts the myoepithelial cells of the alveoli
What is the role of prolactin in breastfeeding?
It enlarges breasts and produces milk
Which hormones are produced in the anterior pituitary gland?
- Thyroid stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Growth hormone (GH)
- Follicle stimulating hormone (FSH)
- Luteinising hormone (LH)
- Prolactin (Prl)
How many different hormones does the anterior pituitary gland produce?
6
Which hormones are produced in the posterior pituitary gland?
- Arginine vasopressin (AVP) (also known as ADH)
- Oxytocin
How many different hormones are produced in the posterior pituitary gland?
2
What are the 5 phenotypically distinct cells of the anterior lobe of the pituitary gland and what % do they make up?
Somatotropes (50%) Lactotropes (10-20%) Corticotropes (5-10%) Thyrotropes (5%) Gonadotropes (10-15%)
What do Somatotropes of the anterior pituitary gland do?
They synthesise growth hormones
What do Lactotropes of the anterior pituitary gland do?
They synthesise prolactin
What do Corticotropes of the anterior pituitary gland do?
They synthesise adrenocorticotropic hormone (ACTH)
What do Thyrotropes of the anterior pituitary gland do?
They synthesise Thyrotropin
What do Gonadotropes of the anterior pituitary gland do?
They synthesise Luteinising hormone (LH) and follicle stimulating hormone (FSH)
What is meant by three levels of endocrine integration?
For hormones to act, they have to go through 3 stages:
- Hypothalamic hormones
- Anterior pituitary hormones
- Endocrine targets
Then the nonendocrine targets are reached. Each hormone goes through each step apart from breast tissue
What molecule supresses the release of prolactin?
Dopamine
What type of steroid hormone is produced in the zona Glomerulsa of the adrenal gland?
Mineralocorticoids
What type of steroid hormone is produced in the zona Fasciculata of the adrenal gland?
Glucocorticoids
What type of steroid hormone is produced in the zona Reticularis of the adrenal gland?
Androgens
What are Glucocorticoids for?
They are:
- anti-inflammatory in all tissues
- control metabolism in muscle, fat, liver and bone
- Affect vascular tone
- Influence mood, behaviour and sleep‒wakefulness cycles
What are Leydig cells for?
They produce testosterone under the control of LH
What is the posterior pituitary gland comprised of?
Axons of cell bodies in the hypothalamus (Supraoptic and paraventricular)
Where are hormones of the posterior pituitary gland synthesised?
In the Supraoptic and Paraventricular nuclei
What is the hypothalamohypophysial tract for?
Axons pass from the hypothalamus to the posterior pituitary through it
Where are hormones synthesised in the posterior pituitary gland stored before they go into circulation?
In vesicles
What is the Hypophysis?
The pituitary gland
What is the function of ADH?
To increase permeability of the collecting ducts to water
Which receptors does ADH work on?
V2 receptors
What are the vasopressor action of ADH and which receptors are used for this?
To constrict smooth muscle cells using V1 receptors
What is Paturition?
Childbirth
What happens to oxytocin sensitivity in late pregnancy?
The myometrium becomes more sensitive to oxytocin (it’s a positive feedback effect)
Describe the positive feedback loop that begins when the foetus drops lower in the uterus
The movement causes the cervix to stretch. The stretching increases oxytocin release from the posterior pituitary which increases prostaglandins in the uterine wall. All this will work to together to cause uterine contractions which cause the cervix to stretch more
What are some acquired defects of the hypothalamic pituitary axis?
Tumours, Trauma, Inflammation
What are some congenital embryopathic defects of the hypothalamic pituitary axis?
Kallman’s syndrome, Pituitary Aplasia, Anencephaly, midline defects
What is Kallman’s syndrome?
Combines an impaired sense of smell with a hormonal disorder that delays or prevents puberty.
It’s due to an underdevelopment of nerves that signal the hypothalamus
What is Pituitary Aplasia?
A rare congenital anomaly which presents with consequences of multiple pituitary hormone deficiency and involves absence of anterior and posterior pituitary gland and the pituitary stalk
What is Anencephaly?
A birth defect in which a baby is born without parts of the brain and skull. It’s usually fatal
What are midline defects?
Defect that occurs on the anterior (front) portion of a body
What are some genetic defects of the Hypothalamis pituitary axis?
Hypothalamic/pituitary hormone gene defects, hormone receptor gene defects
What are some clinical manifestations of lesions of the hypothalamic pituitary axis - tumours?
Headaches, visual field issues, Hypo/Hyperpituitarism
What is syndrome of Panhypopituitarism?
The progressive loss of anterior pituitary function
What is the most common type of pituitary tumour?
A prolactin tumour (Causes no periods and low testosterone)
Which type of pituitary adenoma is treated during pregnancy?
Microadenomas are treated, macroadenomas aren’t
What is Galactorrhoea?
A milky nipple discharge unrelated to the normal milk production of breast-feeding
What are some symptoms of Prolactinomas and why?
Galactorroea, recused gonadal function
Because too much Prolactin is being produced
What is Gonadal function?
Production of sperm and ova
What are the symptoms of ACTH secreting tumours and why?
Centripetal obesity, thin skin, osteoporosis, diabetes
Because too much ACTH is being produced
What is centripetal obesity?
Obesity around the middle which increases the risk of cardiovascular disease
What are the symptoms of GH secreting tumours and why?
Gigantism (Acromegaly)
Because there is too much GH produced
What are the symptoms of FSH/LH secreting tumours?
Hypersecretion syndromes
What are the symptoms of TSHomas and why?
Thyrotoxicosis
Because too much TSH is being secreted
What would be the clinical assessment for someone with suspected pituitary tumours?
- History
- Examination (signs of hormones excess or deficiency)
- Basal hormone results
- Stimulated secretion (to seperate normal from abnormal)
- Visual fields
- Imaging MRI (CT)
How is the Insulin Hypoglycaemia test used to measure pituitary function?
In response to low glucose levels, the pituitary gland will churn out hormones which can be measured