18 Hypothalamus/ Pituitary physiology

Question 1

Which of the following are results of compression by pituitary tumour on itself/ optic chiasm/ cranial nerves?

A. Bitemporal hemianopia
B. Hyperpituitarism
C. Ophthalmoplegia
D. Diplopia

Answer 1

all except B

B: should be hypopituitarism
C = weakness or paralysis of one or more extraocular muscles for eye movement

D = simultaneous perception of 2 images of a single object

Question 2

What is craniopharyngioma? What are the possible symptoms?

Answer 2

Para-pituitary tumour, can compress on stalk/ hypophyseal portal system to produce stalk effect (selective increase in prolactin)

Question 3

Anterior pituitary is under the control of hypothalamus and higher brain centers, for example:
A. internal biological clock
B. stress
C. central glucopenia 
can affect the release of hormones

Answer 3

All of them

Question 4

Which of the followings are inputs converged to the hypothalamus to control posterior pituitary?

A. osmoreceptors
B. baroreceptors
C. stress
D. suckling

Answer 4

All of the above

Question 5

Adrenal medulla is inside/outside of the adrenal cortex.

It is similar to the sympathetic/parasympathetic preganglionic/postganglionic neurons

Answer 5

inside;
sympathetic postganglionic neurons

They are directly innervated by preganglionic neurons of the sympathetic nervous system

Question 6

Adrenal medulla releases 80% of epinephrine and 20% norepinephrine in response to ____________(NT).

Answer 6

acetylcholine from sympathetic preganglionic neurons

Question 7

List the 6 anterior pituitary hormones and their respective hypothalamic hormone.

Answer 7

1. (+1) LH/FSH (Gonadotrophins): from GnRH (Gonadotrophin releasing hormones)
2. GH from GHRH
3. ACTH from CRH (corticotrophin releasing hormone)
4. TSH (Thyroid stimulating hormone) from TRH (Thyrotropin releasing hormone)
5. Prolactin; Dopamine - prolactin inhibiting hormone (TRH, VIP: prolactin releasing hormone)

Question 8

Give 4 reasons for hypopituitarism.

Answer 8

1. Hypophysectomy; irradiation
2. Sheehan’s syndrome: severe postpartum hemorrhage > hypovolemic shock that causes pituitary infarction/necrosis = panhypopituitarism
3. Pituitary tumour - mass effect
4. Compression on pituitary stalk > selective rise in prolactin

Question 9

Which of the following are stimulatory to the release of prolactin?

A. Sleep
B. Stress
C. Suckling
D. Dopamine
E. TRH
F. VIP
G. Estrogen

Answer 9

All except D

G: during pregnancy, estrogen stimulates prolactin synthesis and secretion, giving rise to hypertrophy and hyperplasia of lactotrophs

Question 10

1. Mammogenesis (puberty)
   ○ Mammary ductal growth under _________ and ________effects
2. Mammogenesis (sexual maturation + pregnancy)
   ○ Growth of mammary ducts and lobulo-alveolar structures under combined effects of __________ and _____________in each menstrual cycle + _________during pregnancy

Answer 10

1. estrogen + GH

2. estrogen + progesterone; prolactin

Question 11

3. Lactogenesis I
   ○ Secretory differentiation of lubulo-alveolar structures under ____________ effect for milk production preparation
4. Lactogenesis II
   Initiation and maintenance of milk production under effect of _____________

Answer 11

3. prolactin;

4. prolactin

Question 12

What is the problem with high levels of prolactin?

Answer 12

Prolactin increase will knock down GnRH levels and thus FSH and LH, resulting in hypogonadism in men and in women;
also cause gynaecomastia (enlargement of men’s breast)/ galactorrhea (spontaneous flow of breast milk)

Question 13

How can high prolactin levels be treated?

Answer 13

Use dopamine D2 receptor agonists (bromocriptine/ cabergoline)

Question 14

What are the 2 main posterior pituitary hormones?

Answer 14

Vasopressin/ADH

and oxytocin

Question 15

What is the risk in having high dose of oxytocin to induce labour?

Answer 15

High dose oxytocin infusion to induce labour may result in water intoxication due to shared anti-diuretic effect (with vasopressin) in causing water retention

Question 16

What are the effects of binding to the 3 different vasopressin receptors?

Answer 16

V1 receptor: Vasopressor effect on vascular smooth muscles
(raise in blood pressure)

V2 receptor: Antidiuretic effect on renal collecting duct

V3 receptor: AVP (+CRH) as hypothalamic releasing hormone can stimulate ACTH secretion

Question 17

What will happen when there is ADH deficiency?

Answer 17

It will cause diabetes insipidus.

Question 18

How can central and nephrogenic DI be differentiated?

Answer 18

Use water deprivation test with desmopressin.
Water deprived for 8 hours > injection of desmopressin (synthetic ADH)
Central DI: will respond (decrease in plasma osmolarity)
while nephrogenic DI will not.

Question 19

The controls of release of oxytocin include neuroendocrine reflex (+ve feedback), Ferguson reflex (stretching of cervix) and milk ejection reflex by suckling of breasts.

What are the 3 main effects of oxytocin?

Answer 19

1. Uterine smooth muscle contraction
2. Myoepithelial cell contraction
3. Promote maternal behaviour

Question 20

Describe the positive feedback mechanism of oxytocin secretion. (3 steps)

Answer 20

1. Uterine contraction at onset of parturition apply mild stretch to cervix
2. Sensory input from the cervix causes oxytocin release from posterior pituitary gland
3. Stimulates further contraction of the uterus, and stimulate more oxytocin secretion again

Question 21

Which of the following example(s) is/are neuroendocrine reflex?

A. Suckling-induced oxytocin secretion
B. Suckling-induced prolactin secretion
C. Release of oxytocin in labour

Answer 21

All of the above