Hypothalamus and Pituitary Axis Flashcards Preview

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Flashcards in Hypothalamus and Pituitary Axis Deck (15)
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1
Q

thyrotropes

A

TSH alpha beta dimer

2
Q

somatotropes

A

growth hormones; 191 a.a. protein

3
Q

corticotropes

A

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

4
Q

lactotropes

A

prolactin; 191 a.a. protein

5
Q

gonadotropes

A

FSH and LH; alpha beta dimers

6
Q

Neurohormones released from the posterior pituitary

A

– Oxytocin (OXT;9a.a.peptide)

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

7
Q

. Neurohormones controlling anterior pituitary hormones

A
– Prolactin releasing hormone 
– Prolactin-inhibiting hormone
– Thyrotropin-releasing hormone
– Corticotropin-releasing hormone 
– Growth hormone-releasing hormone 
– Somatostatin 
– Gonadotropin-releasing hormone
8
Q

Physiological actions of Growth Hormone - DIRECT ANTI-INSULIN

A
  • increased lipolysis in adipose tissue
  • increased blood glucose (both due to decreased glucose uptake in muscle and adipose tissue; antagonised by insulin release
9
Q

Physiological actions of Growth Hormone - INDIRECT ACTIONS

A

this is IGF-1 Release from the liver

  • increased cartilage formation and bone growth
  • increased general protein synthesis and cell growth/division
10
Q

Physiological consequences of the growth hormone

A
  • 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
11
Q

what happens when you have a GH deficiency

A
  • 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

12
Q

what happens if you have surplus GH

A

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

13
Q

what are the physical signs of gigantism and acromegaly

A
  • 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
14
Q

associated symptoms of gigantism and acromegaly

A
  • 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%)
15
Q

Oxytocin (OXT)

A
  • 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