Hypothalamus and Pituitary Axis

Question 1

thyrotropes

Answer 1

TSH alpha beta dimer

Question 2

somatotropes

Answer 2

growth hormones; 191 a.a. protein

Question 3

corticotropes

Answer 3

adrenocorticotropic hormone (ACTH); 39 a.a. peptide from pro-opiomelanocortin (POMC)

Question 4

lactotropes

Answer 4

prolactin; 191 a.a. protein

Question 5

gonadotropes

Answer 5

FSH and LH; alpha beta dimers

Question 6

Neurohormones released from the posterior pituitary

Answer 6

– Oxytocin (OXT;9a.a.peptide)

- Vasopressin (AVP) also called anti-diuretic hormone (ADH; 9 a.a. peptide)

Question 7

. Neurohormones controlling anterior pituitary hormones

Answer 7

– Prolactin releasing hormone 
– Prolactin-inhibiting hormone
– Thyrotropin-releasing hormone
– Corticotropin-releasing hormone 
– Growth hormone-releasing hormone 
– Somatostatin 
– Gonadotropin-releasing hormone

Question 8

Physiological actions of Growth Hormone - DIRECT ANTI-INSULIN

Answer 8

• increased lipolysis in adipose tissue
• increased blood glucose (both due to decreased glucose uptake in muscle and adipose tissue; antagonised by insulin release

Question 9

Physiological actions of Growth Hormone - INDIRECT ACTIONS

Answer 9

this is IGF-1 Release from the liver

• increased cartilage formation and bone growth
• increased general protein synthesis and cell growth/division

Question 10

Physiological consequences of the growth hormone

Answer 10

• increased linear growth and lean body mass (important for normal post-natal development and rapid growth through puberty)
• maintains protein synthesis and tissue functions in adults

Question 11

what happens when you have a GH deficiency

Answer 11

• dwarfism in children due to predictable effects on linear bone growth and decreased availability of lipids and glucose energy

this can be treated effectively with recombinant GH therapy

Question 12

what happens if you have surplus GH

Answer 12

acromegaly often due to pituitary adenoma

if it happens before puberty…
- gigantism due to excess stimulation of epiphyseal plates

After puberty (there can be no stimulation of linear growth due to the fusion of epiphyses)

• periosteal bone growth causing enlarged hand, jaw and foot size
• soft tissue growth leading to enlargement of the tongue and coarsening of the fascial features
• insulin resistance and glucose intolerance (diabetes)

CAN TREAT with synthetic long-acting somatostatins (octreotide) until transphenoidal surgery

Question 13

what are the physical signs of gigantism and acromegaly

Answer 13

• Gradual enlargement of hands and feet
• Rapid growth (in some cases >6ft by 12 yrs; >8ft as adult)
• Swelling of soft tissue
• Skin tags (wart-like growths)
• Muscle weakness/fatigue
• Skin changes, including thickening, oiliness, acne
• Hirsutism (abnormal hair growth)
• Coarsening of facial features, including forehead, nose, lips, tongue and jaw

Question 14

associated symptoms of gigantism and acromegaly

Answer 14

• Arthralgia (pain in joints) (75%)
• Amenorrhea in women (72%)
• Hyperhidrosis (excessive perspiration (64%)
• Sleep apnoea (temp. stopping of breathing during sleep) (60%)
• Headaches (55%)
• Paraesthesia or carpel tunnel syndrome (40%)
• Loss of libido or impotence (36%)
• Hypertension (28%)
• Thyroid disorders (21%)
• Visual field defects (19%)

Question 15

Oxytocin (OXT)

Answer 15

• Produced by hypothalamic neurons in the paraventricular and supraoptic nuclei
• Bound by neurophysin I and carried in the axons to the posterior pituitary
• Release is controlled directly by nervous impulses form the hypothalamus