Endocrinology

Question 1

Functions of the pancreas

Answer 1

Exocrine function - secretion of digestive enzymes directly into the GI tract

Endocrine function - secretion of insulin into the blood

Question 2

Functions of the different parts of the adrenal glands

Answer 2

Medulla - stress response

Cortex - stress, sodium and glucose homeostasis

Question 3

What does the anterior pituitary gland secrete?

Answer 3

Stimulating (or trophic) hormones

TSH

ACTH - adrenocorticotrophic hormone

FSH
LH

GH

Prolactin

Question 4

What does the hypothalamus secrete?

Answer 4

Releasing hormones which control the secretion of hormones from the anterior pituitary

TRH (thyrotrophin releasing hormone)

CRH - cotricotrophin releasing hormone

GnRH (gonadotrophin releasing hormone)

GHRH - growth hormone releasing hormone

These releasing hormones travel straight down from the hypothalamus to the anterior pituitary and do not enter the systemic circulation.

Question 5

How is the endocrine release of hormones controlled?

Answer 5

Hypothalamic hormones stimulate release of anterior pituitary hormones which stimulate release of hormones from target organs

Hormones from target organs provide negative feedback to decrease secretion of hypothalamus and pituitary hormones
e.g. Cortisol decreases the secretion of CRH and ACTH

Question 6

What does the posterior pituitary secrete?

Answer 6

ADH (anti-diuretic hormone, also called vasopressin)
Oxytocin

These are both synthesised in the hypothalamus and converted to active hormone within the posterior pituitary

Question 7

What influences the secretion of ADH?

Answer 7

Plasma osmolarity

Decreased blood volume and increased blood osmolality increase ADH secretion

Question 8

How does ADH work?

Answer 8

Stimulation of v2 receptors causes translocation of aquaporins to the membrane of the kidney tubule, thus allowing water reabsorption.

Stimulation of v1 receptors causes vasoconstriction.
(this doesn’t occur at physiological concentrations)

Question 9

What are the functions of oxytocin?

Answer 9

Positive feedback loops:

In labour stimulation of cervix/vagina causes release of oxytocin which causes contraction of myometrium and further expulsion of the foetus and further stimulation of the cervix/vagina

In breastfeeding, nipple stimulation causes oxytocin release which causes muscle contraction and milk let down leading to suckling etc…

Question 10

Control of prolactin secretion

Answer 10

Different to other pituitary hormones

It is under tonic inhibition by dopamine

Prolactin secretion is stimulated by mild stress, nipple stimulation and coitus

Question 11

Control of GH release

Answer 11

Growth hormone releasing hormone (GHRH) - more important in control

and Growth hormone release inhibiting hormone (GHRIH/somatostatin)

Question 12

What stimulates the secretion of growth hormone?

Answer 12

Decreased carbohydrates and fatty acids and increased amino acids

Question 13

What element does T3 and T4 synthesis require?

Answer 13

Iodine

Question 14

Four types of thyroid cancer which is the most common?

Answer 14

Papillary (most common 75-85%) - increased risk of LN metastasis

Follicular - 10-20%, metastasises to bone, lung and liver
Medullary - arises from C cells, associated with MEN2 syndrome
Anaplastic <5% older patients, poor prognosis

Question 15

Function of the parathyroid gland

Answer 15

Secretes PTH

Which controls calcium levels in the blood

Question 16

Hormones released by different parts of the adrenal cortex

Answer 16

Salt, sugar and sex and GFR mnemonics

Zona Glomerulosa - Mineralocorticoid, for the absorption of sodium –> aldosterone is produced

Zone fasciculata - glucocorticoids –> cortisol is produced

Zona reticularis - Sex hormones –> androgens produced –> dihydrotestosterone and oestradiol are produced

Question 17

What do medulla of adrenal glands also secrete?

Answer 17

Medulla cells secrete adrenaline and smaller amounts of noradrenaline – i.e. catecholamines

Question 18

What is a phaeochromocytoma?

Answer 18

Tumour of the adrenal medulla

Question 19

If Hypertension and hypokalaemia, younger or restistant hypertension what may be the cause of hypertension?

Answer 19

Conn’s syndrome

Question 20

Describe the secretion of ACTH

Answer 20

Pulsatile secretion:
Peaks early in the morning (upon waking), nadir in the middle of the night

Cortisol secretion shows the same pattern except shifted later by approximately 2h.

Increased secretion at times of prolonged stress

Disrupted pattern can occur due to shift work and long-haul travel