T1 L3, Pituitary gland Flashcards by Malgorzata Szymaniak

What type of circulation does the pituitary gland have?

Sinusoidal circulation (containing pores that allow free flow of proteins)

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Which gland sits right below the optic chiasm?

The pituitary gland

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Which structure is the pituitary gland directly attached to?

The hypothalamus. They’re connected by the stalk

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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

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Which Hypothalamic releasing hormones stimulates secretion of FSH and LH?

Gonadatropin releasing hormone (GnRH)

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Which Hypothalamic releasing hormone inhibits growth hormone secretion?

Somatostatin (SS)

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Which Hypothalamic releasing hormones inhibits prolactin secretion?

Dopamine

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Which Hypothalamic releasing hormone stimulates secretion of ACTH?

Corticotropin releasing factor (CRF)

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What is ACTH?

Adrenocorticotropic hormone which controls the production of cortisol

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Which Hypothalamic releasing hormone stimulates secretion of TSH?

Thyrotropin releasing hormone (TRH)

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Which Hypothalamic releasing hormones stimulates secretion of GH?

Growth hormone releasing hormone (GHRH)

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What is GH?

Growth hormone. It fuels childhood growth and helps maintain tissues and organs throughout life

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How are hormones from the hypothalamus delivered to the anterior pituitary gland?

Through the hypothalamic-hypophyseal portal system

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How does prolactin act as a natural contraceptive?

It stops ovulation

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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

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What is the role of prolactin in breastfeeding?

It enlarges breasts and produces milk

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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)

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How many different hormones does the anterior pituitary gland produce?

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Which hormones are produced in the posterior pituitary gland?

Arginine vasopressin (AVP) (also known as ADH)

- Oxytocin

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How many different hormones are produced in the posterior pituitary gland?

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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%)

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What do Somatotropes of the anterior pituitary gland do?

They synthesise growth hormones

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What do Lactotropes of the anterior pituitary gland do?

They synthesise prolactin

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What do Corticotropes of the anterior pituitary gland do?

They synthesise adrenocorticotropic hormone (ACTH)

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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