Adrenal Glands

State the hormones produced by the hypothalamus

GnRH, GHRH, **, TRH, DA and CRH

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State the hormones released by anterior pituitary

FSH/LH, growth hormone, TSH, prolactin and ACTH

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The hormones produced which responses in the organs? (1)

FSH/LH (gonads, germ cell development, secrete hormones oestrogen/progesterone/testosterone). GH (liver, secrete IGF-I, tissues, protein synthesis/carbohydrate/lipid metabolism). TSH (secrete thyroxine, triiodothyronine)

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The hormones produced which responses in the organs? (2)

Prolactin (breast development, milk production, facilitate reproductive function in males), ACTH (adrenal cortex secretes cortisol)

4 of 25

Where are the adrenal glands located?

Superior (above) to kidneys. Suprarenal glands. 2 glands

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Describe a cross-section of a human adrenal (1)

Consists of cortex and medulla. Cortex secretes steroid hormones (e.g. glucocorticoids, mineralcorticoids). Medulla is a source of catecholamines (e.g. adrenaline, noradrenaline, dopamine) - extension of sympathetic NS

6 of 25

Describe a cross-section of a human adrenal (2)

Cortex consists of zona glomerulosa (secretes aldosterone), zona fasciculata and zona reticularis (secrete cortisol and androgens). Medulla secretes adrenaline and noradrenaline

7 of 25

What is the precursor for steroid hormones?

Cholesterol (needed to synthesis of aldosterone, cortisol, testosterone, oestradiol)

8 of 25

Describe features of aldosterone

Mineralocorticoid. Major role in control of electrolyte homeostasis. Increases Na reabsorption and K excretion in kidney. Increases blood volume and pressure. Regulated by RAAS

9 of 25

Describe features of cortisol

Glucocorticoid. Major role in response to 'stress'. Effects on metabolism, CV (influence blood flow/pressure), inflammatory and immune responses

10 of 25

Describe the mechanism of action for cortisol

Diffuses across membrane and into the cell. Protein unbound from intracellular receptor. Cortisol binds to intracellular receptor in the cytoplasm. Complex enters the nucleus. Transcription takes place and mRNA production occurs

11 of 25

What are the metabolic effects of cortisol?

Effects on metabolism to - increase protein catabolism (muscle), increase gluconeogenesis (liver), increase plasma glucose, stimulate caloric intake and favours deposition of fat in selected sites

12 of 25

How does cortisol effect the inflammatory and immune systems?

Inhibition of inflammatory responses (inhibits recruitment of neutrophils and release of PGs). Suppression of immune response (inhibits proliferation of thymus-derived lymphocytes)

13 of 25

Describe features of androgens

E.g. DHEA, androstenedione. May be involved in the development secondary sexual characteristics at puberty. Role in preventing degenerative changes in ageing

14 of 25

Describe the control of adrenal function - response to reduced plasma volume (1)

Renin released by kidney nephrons in response to reduced plasma volume. Renin converts angiotensinogen to ang I which is converted to ang II in tissues. Ang II acts on glomerulosa cells to stimulate aldosterone production

15 of 25

Describe the control of adrenal function- response to reduced plasma volume (2)

Aldosterone increases Na reabsorption and results in increasing plasma volume

16 of 25

Describe the control of adrenal function - response to stress (1)

ACTH released from anterior pituitary in response to stress. ACTH binds to receptors in faciculata and reticularis cells and stimulates cortisol production. Cortisol affects metabolism (catabolic). Cortisol is anti-inflammatory

17 of 25

Describe the control of adrenal function - response to stress (2)

Cortisol has an inhibitory feedback on the hypothalamus and pituitary

18 of 25

Outline the feedback control of anterior pituitary

Stress/other factors-hypothalamus-secrete CRH (neuroendocrine peptide)-stimulate anterior pituitary-secrete ACTH (endocrine polypeptide)-stimulate adrenal cortex-secrete cortisol-actions (cortisol inhibits hypothalamus/anterior pituitary)

19 of 25

Give examples of adrenal disorders

Congenital adrenal hyperplasia. Addison's disease. Cushing's syndrome

20 of 25

Describe features of congenital adrenal hyperplasia

Deficiency (usually fatal if untreated). Enzyme deficiencies - no hormones. Most serious (no cholesterol) - no sexual differentiation. Others (e.g. 11b hydroxylase) - salt loss, hypertension, absent/precocious puberty

21 of 25

Describe features of Addison's disease

Acquired deficiency. TB or autoimmune destruction. Severe illness with hypotension, tiredness, weakness, anorexia, vomiting. Treated by steroid replacement

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Describe features of Cushing's syndrome (1)

Overproduction. Excess of glucocorticoids. Tumour in pituitary or adrenal glands (over production of CRH or ACTH). Clinical steroid administration

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Describe features of Cushing's syndrome (2)

Gluconeogenesis, peripheral insulin resistance, enhanced glucagon release/suppression of insulin release. Catabolism (loss in muscle and bone protein, thinning of skin). Weight gain, redistribution of fat to abdomen/face/posterior neck

24 of 25

Describe features of Cushing's syndrome (3)

Dyslipidemia (related to direct/indirect effect of cortisol to increase lipolysis, VLDL synthesis, fatty accumulation in liver). Reduce wound healing and increased bruising

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Adrenal Glands

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