Endocrinology Flashcards
What are the main endocrine glands?
- Hypothalamus/Pituitary
- Thyroid
- Parathyroid
- Pancreas
- Adrenal
- Ovaries/Testicles
What connects the hypothalamus to the pituitary gland?
Pituitary stalk
What are the two lobes of the pituitary gland?
Anterior pituitary and posterior pituitary
What is the function of the anterior pituitary?
Produces various hormones
What is the function of the posterior pituitary?
Stores various hormones
What 5 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 is the purpose of the growth hormone?
For skeletal growth
What is the purpose of the adrenocorticotrophic hormone (ACTH)?
Stimulates the adrenals to produce steroids
What is the purpose of the gonadotrophin hormones?
Stimulate the testicles or ovaries to produce sex hormones
What is the purpose of the thyroid stimulating hormone (thyrotrophin-TSH)?
Stimulates the thyroid to produce thyroid hormones
What is the purpose of prolactin (PRL)?
Stimulates breast milk production
What are the two hormones (produced by the hypothalamus) that the posterior pituitary gland stores?
- Antidiuretic hormone (ADH)
- Oxytocin
What is the function of ADH?
Stimulates water reabsorption by the kidneys
What is the main function of oxytocin?
helps uterine contractions during labour
How does the hypothalamus control the anterior pituitary gland?
The hypothalamus releases a hormone which promotes the secretion of hormones from the anterior pituitary gland (hypothalamus-pituitary axis).
What 4 hormones secreted from the hypothalamus promote the release of hormones in the anterior pituitary gland?
- Corticotrophin releasing hormone (CRH)
- Growth hormone releasing hormone (GHRH)
- Thyrotropin releasing hormone (TRH)
- Gonadotrophin releasing hormone (GnRH)
What does corticotrophin releasing hormone (CRH) stimulate?
ACTH secretion
What does growth hormone releasing hormone (GHRH) stimulate?
GH secretion
What does thyrotropin releasing hormone (TRH)
stimulate?
TSH secretion
What does gonadotrophin releasing hormone (GnRH) stimulate?
FSH & LH secretion
What is special about prolactin releasing hormone?
Does not exist and prolactin is under the inhibitory effect of the hypothalamus
How are pituitary hormones switched off by negative feedback?
- Cortisol switches off ACTH and CRH
- Growth hormone, switches of GH and GHRH
- Thyroid hormones switch off TSH and TRH
- Sex hormones switch off FSH/LH and GnRH
Which glands are not controlled by the pituitary?
- Adrenal medulla
- Parathyroid
- Pancreas
- Gut hormones
What does the adrenal medulla do?
Produces adrenaline and noradrenaline
What does the parathyroid do?
Controls calcium levels
What does the pancreas do?
controls sugar levels
Which gland does the adrenocorticotrophic hormone affect?
Adrenals (steroids)
Which gland does the thyroid stimulating hormone affect?
Thyroid (T3 and T4)
Which organ does FSH/LH affect?
Ovary/testicle (sex hormones)
What is the thyroid composed of?
- Midline isthmus (just below the cricoid cartilage)
- Right lobe
- Left lobe
How are thyroid cells arranged and what type of cells do they contain?
- arranged in follicles that produce thyroid hormones
- contain C cells producing calcitonin for calcium metabolism
What do thyroid hormones do by interacting with their receptors in various organs?
- Regulate gene expression
Regulate various aspects of organ function
Control of thyroid hormone secretion
TRH is secreted by the hypothalamus.
Causes the pituitary gland to secrete TSH.
Causes the thyroid to secrete thyroid hormones (T3 and T4).
Decrease in thyroid hormones is picked up by hypothalamus and pituitary which secretes more hormones. Negative feedback.
Which gland is the metabolism of calcium controlled by?
Mainly controlled by 4 parathyroid glands sitting behind the thyroid
What are other organs involved in calcium metabolism (and how)?
- Kidneys = calcium excretion and production of active Vitamin D
- Gut = Absorption of calcium
- Bone = Storage of calcium
- Thyroid
Where are the adrenal glands situated?
Above the kidneys
What are the adrenal glands composed of?
- Adrenal cortex = 90% of the gland
- Adrenal medulla = 10% of the gland
What does the adrenal cortex produce?
- Corticosteroids (cortisol)
- Androgens (male hormones)
- Mineralocorticoid (aldosterone)
What does the adrenal medulla produce?
- Catecholamines (adrenaline, noradrenaline and dopamine)
Which two hormone secretions related to blood pressure is not controlled by the pituitary?
- Catecholamine secretion
- Mineralocorticoid secretion (related to renin-angiotensin system, which controls blood pressure)