Introduction to Endocrine

Question 1

What hormone is released by the pineal gland and what are its 3 roles?

Answer 1

Melatonin

Regulates circadian rhythm, involved in maintaining immune function and acts as an antioxidant

Question 2

What hormone is released by the parathyroid glands and what is its role?

Answer 2

PTH

Increases plasma calcium and decreases plasma phosphate levels

Question 3

What hormones are released by the thymus and what are their roles?

Answer 3

Thymosin and thymopoietin

Involved in lymphocyte development

Question 4

What hormone is released by the heart and what is its role?

Answer 4

Atrial natriuretic peptide

Acts on the kidneys to increase Na+ excretion

Question 5

What hormones are released by the liver and what are their roles?

Answer 5

Angiotensinogen: acts on adrenal cortex to stimulate aldosterone secretion, and on blood vessels to cause vasoconstriction and increase BP
IGFs: act on many tissues, involved in growth promotion

Question 6

Where does an autocrine signal act?

Answer 6

On the same cell that secreted it

Question 7

Where does a paracrine signal act?

Answer 7

Diffuses to act on adjacent cells

Question 8

What is a neurohormone? What are the 3 major groups of neurohormones?

Answer 8

A neurocrine signal secreted into the bloodstream
Hypothalamic neurohormones acting on the anterior pituitary, hypothalamic neurohormones acting on the posterior pituitary, and catecholamines made by modified adrenal medulla neurons

Question 9

What is a tropic hormone?

Answer 9

A hormone that controls the secretion of another hormone

Question 10

What is a trophic hormone?

Answer 10

Usually a hormone that stimulates growth and development

Question 11

Are peptide hormones made on demand or stored in advance?

Answer 11

Precursor stored in advance

Question 12

What is the difference peptide and steroid hormones in terms of their half-life?

Answer 12

Steroid hormones have a longer half-life than peptide hormones

Question 13

Do thyroid hormones resemble peptide or steroid hormones in terms of their structure and action?

Answer 13

Steroid

Question 14

Do catecholamines resemble peptide or steroid hormones in terms of their structure and action?

Answer 14

Peptide

Question 15

What are the amine hormones mostly derived from?

Answer 15

Tyrosine

Question 16

List 4 factors influencing the plasma concentration of free, biologically active hormone

Answer 16

Rate of secretion
Rate of metabolic activation (only for a few hormones)
Extent of binding to plasma proteins (for steroid and thyroid hormones)
Rate of metabolic inactivation and excretion

Question 17

How are steroid hormones removed from the circulation?

Answer 17

They are conjugated and removed via the urine and bile

Question 18

How are amine hormones removed from the circulation?

Answer 18

They are degraded by specific circulating degrading enzymes

Question 19

How are large peptides removed from the circulation?

Answer 19

Via receptor-mediated endocytosis

Question 20

How are most small peptides removed from the circulation?

Answer 20

Via the kidneys

Question 21

What is the role of antagonism in hormone regulation? Give an example

Answer 21

The hormones act together but in opposite directions, which allows for fine tuning (e.g. insulin and glucagon)

Question 22

What is synergism in terms of hormone regulation? Give an example

Answer 22

Multiple stimuli producing an effect that is more than additive (e.g. glucagon, cortisol and adrenaline in the control of blood glucose)

Question 23

What does “permissive” refer to in terms of hormone action? Give an example

Answer 23

1st hormone requires the presence of a 2nd hormone to exert its effects (e.g. cortisol and adrenaline, thyroid hormone and IGFs)

Question 24

What is the difference between a primary and secondary endocrine disorder?

Answer 24

In a primary endocrine disorder, the gland is abnormal

In a secondary endocrine disorder, the gland is abnormal but the tropic hormone is abnormal

Question 25

What are the advantages of the hypothalamic-hypophyseal portal system between the hypothalamus and the anterior pituitary?

Answer 25

Less hormone secretion is required to elicit a response | There is direct delivery of hormone

Question 26

What is another name for the posterior pituitary? How is this related to its embryological origin?

Answer 26

Neurohypophysis | An outgrowth of the brain, composed of nervous tissue

Question 27

What is another name for the anterior pituitary? How is this related to its embryological origin?

Answer 27

Adenohypophysis | Originated from glandular epithelial tissue and ectodermal cells (true endocrine gland)

Question 28

What is the infundibulum?

Answer 28

The stalk connecting the pituitary to the brain

Question 29

What 2 hormones are released by the posterior pituitary?

Answer 29

Vasopressin/ADH | Oxytocin (OT)

Question 30

What is the role of ADH?

Answer 30

Increases collecting duct permeability to decrease urinary output

Question 31

What is the role of OT?

Answer 31

Causes ejection of milk by the breasts, and contraction of the uterus

Question 32

What nuclei are involved in the control of the posterior pituitary?

Answer 32

Supraoptic and paraventricular nuclei

Question 33

What nuclei are involved in control of the anterior pituitary?

Answer 33

Arcuate and other nuclei

Question 34

List 7 hormones secreted by the hypothalamus to target the anterior pituitary

Answer 34

``` CRH TRH GnRH GHRH GHIH (somatostatin) PRF PIH (dopamine) ```

Question 35

What are somatomedins?

Answer 35

IGFs

Question 36

List 8 hormones secreted by the anterior pituitary

Answer 36

``` ACTH B-lipotropin TSH (thyrotropin) Prolactin LH FSH GH ```

Question 37

Which hypothalamic hormone, besides PRF, can stimulate prolactin secretion from the anterior pituitary?

Answer 37

TRH

Question 38

Besides tropic hormones, what other controls can affect hormone production?

Answer 38

Higher centres in the brain | Changes in diurnal/circadian rhythm

Question 39

What causes Kallman syndrome? What are the symptoms?

Answer 39

The failure of embryological GnRH neurons to migrate via the olfactory pathway Causes hypogonadotropic hypogonadism, and hyposmia/anosmia

Question 40

What % of brain growth occurs in the first 2 years of life?

Answer 40

Postnatal growth spurt results in 70% of brain growth

Question 41

What occurs during the pubertal growth spurt?

Answer 41

Lengthening and epiphyseal fusion of long bones | Production of testosterone and oestrogen

Question 42

What are the metabolic effects of GH?

Answer 42

Increase blood fatty acid and glucose (anti-insulin) | Increase protein synthesis

Question 43

What effect does GH have on soft tissues and the skeleton?

Answer 43

Hyperplasia and hypertrophy of cells

Question 44

What effect does GH have on the liver?

Answer 44

Stimulates production and release of IGFs

Question 45

What hormone is responsible for closing the epiphyseal plates of long bones? (Think about the timing of epiphyseal fusion)

Answer 45

Oestrogen

Question 46

What are the 4 actions of IGFs?

Answer 46

Insulin-like activity (opposes GH) Anti-lipolytic activity (opposes GH) Protein synthesis Epiphyseal growth

Question 47

What is the role of GH in early growth?

Answer 47

Plays a permissive role (required from birth)

Question 48

What is the effect of GH deficiency in children?

Answer 48

Dwarfism

Question 49

What is the cause of Laron dwarfism?

Answer 49

GH receptors are unresponsive despite normal GH

Question 50

What are the effects of adult onset GH deficiency?

Answer 50

Few effects

Question 51

How is GH deficiency treated?

Answer 51

Using genetically engineered hGH

Question 52

List 6 GH-independent causes of short stature

Answer 52

``` Cretinism (TH deficiency) Precocious/early puberty Gonadal dysgenesis (XO chromosomes) Constitutional delayed/stunted growth Psychosocial dwarfism (due to chronic abuse or neglect) Achondroplasia ```

Question 53

What is achondroplasia and what is the underlying cause?

Answer 53

The most common form of dwarfism | Caused by FGFR-3 mutation

Question 54

What is the result of GH excess in childhood vs adulthood?

Answer 54

Gigantism in childhood | Acromegaly in adulthood

Question 55

What are the clinical signs of acromegaly?

Answer 55

Bone and soft tissue deformities | Increased viscera size and protein content