Pituitary, Adrenal & Thyroid Glands Flashcards
The endocrine system is a collection of glands that produce and secrete _____________.
Hormones
What are the 9 major glands of the endocrine system?
- Hypothalamus
- Pituitary
- Thyroid
- Parathyroid
- Adrenals
- Pineal
- Pancreas
- Ovaries
- Testes
What are hormones?
Chemical messengers that travel in the bloodstream, sometimes bound to proteins to help transport them to their target cells.
What are the 3 classes of hormones?
- Steroid hormones - Lipophilic (e.g. Cortisol)
- Peptide hormones - Hydrophilic (e.g. Oxytocin, Insulin)
- Amino acid derived hormone- Hydrophilic (e.g. Thyroid hormone)
Why is the pituitary gland called the “master gland”?
Because it secretes hormones that control the actions of other endocrine glands and tissues throughout the body.
Where is the pituitary gland in the body?
It is a pea-sized oval structure that is suspended under the brain by the pituitary stalk and sits within a narrow opening of the sphenoid bone.
Which other gland is the pituitary gland closely associated with and why?
It is closely associated with the hypothalamus, which releases hormones in response to environmental stimuli that control the synthesis and release of the hormone of the pituitary gland.
How many lobes does the pituitary gland have and what are they called?
It has two lobes, anterior pituitary and posterior pituitary
What does the pineal gland produce?
The pineal gland produces melatonin, which plays a role in sleep patterns and circadian rhythms.
What tissue does the posterior pituitary consist of?
Nervous tissue
What tissue does the anterior pituitary consist of?
Glandular epithelial tissue
Which gland controls the release of peptide hormones from anterior or posterior pituitary?
Hypothalamus
___________ pituitary connects by neural pathway.
Posterior
___________ pituitary connects by unique vascular link.
Anterior
What hormones are released by the posterior pituitary?
- Oxytocin hormone
- Anti-diuretic (vasopressin) hormone
What hormones are released by the anterior pituitary?
- ACTH
- TRH
- GH
- Prolactin
- FSH
- LH
- MSH
What is oxytocin and where is it produced?
Oxytocin is a hormone that plays an important role in the female reproductive system, particularly with childbirth and breast-feeding. It is produced by the posterior pituitary.
What are the functions of oxytocin in women?
- Contraction of the uterine muscle to help expel infant during childbirth
- Promotes ejection of milk from mammary glands during breast feeding; secretion increased by suckling
- Influences social behaviour; Mating/bonding with infant/relationships
- Injection (Syntocinon) used to induce labour and prevent postpartum haemorrhage
What is Vasopressin and where is it produced?
Vasopressin is used to manage anti-diuretic hormone deficiency (also called Anti-Diuretic Hormone). It is produced by the posterior pituitary.
What are the two main functions of Vasopressin?
- Enhances retention of water by nephrons during urine formation (anti-diuretic)
- Contraction of arteriolar smooth muscle (vessel pressor effect)
How does Vasopressin enhance retention of water by nephrons during urine formation?
- Bind to V2 receptor causing an increase in water permeability in distal tubule and collecting ducts leading to increased water reabsorption
- Primary regulator of water balance (urinary)
How does Vasopressin cause contraction of arteriolar smooth muscle (vessel pressor effect)?
- Binds to V1 receptor causing an increase in vasoconstriction
- Plays a minor role in regulating blood pressure
What causes Diabetes Insipidus?
It is caused by a lack of vasopressin (ADH)
What are the main symptoms of Diabetes Insipidus?
- Polyuria (excessive dilute urine >2L/day)
- Polydipsia
What does polyuria mean?
The passage of large volumes of urine with an increase in urinary frequency.
What does polydipsia mean?
Medical definition of excess thirst.
What happens if diabetes insipidus is left untreated?
It leads to shock-like symptoms- Hypotension, tachycardia, tachypnea etc. and can lead to hypernatremia.
What are the treatment options for diabetes insipidus?
- Vasopressin injection
- Desmopressin injection/tablet/nasal spray (no longer acting and has no effect on V2 receptors so no vasoconstriction)
The five cell types in the anterior pituitary secrete 6 major hormones. What are they?
- Somatotropes- GH (Growth hormone (somatotropin))
- Thyrotropes- TSH (Thyroid stimulating hormone)
- Corticotropes- ACTH (Adrenocorticotrophic hormone)
- Gonadotropes- FSH (follicle stimulating hormone) and LH (luteinising hormone)
- Lactotropes- PRL (prolactin)
