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07. Endocrine > 7.02 Pituitary Function > Flashcards

7.02 Pituitary Function Flashcards

1
Q

What are the two parts of the pituitary gland? Give their alternate names too

A
  1. Posterior Pituitary (neurohypophysis)
  2. Anterior Pituitary (adenohypophysis)
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2
Q

Despite being structurally linked to each other as the pituitary gland, how are the anterior and posterior pituitary different to one another?

A

The anterior and posterior pituitary glands can be considered two completely different structures.

  • Embryologically
  • Structurally
  • Functionally different
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3
Q

Describe the posterior pituitary in terms of tissue and the link to the hypothalamus

A

It is a neural tissue

  • Outgrowth of brain, nervous tissue
  • Neural link to hypothalamus
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4
Q

Describe the anterior pituitary in terms of tissue and the link to the hypothalamus

A

Glandular

  • Origin from glandular epithelial tissue, ectodermal cells
  • Vascular link to hypothalamus
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5
Q

Draw the relationship of the hypothalamus to the pituitary gland and the anatomy surrounding it

A
  • The pituitary gland hangs off the hypothalamus
  • The infundibulum is a stalk that connects the pituitary to the hypothalamus
  • The pituitary gland sits in the sella turcica of the body of the sphenoid bone (a well protected gland)
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6
Q

Describe the general flow of information (neural and hormonal) through the pituitary

A
  • From the hypothalamus (trophic hormones)
  • To the anterior/posterior pituitary gland (trophic hormones)
  • To endocrine glands (hormones)
  • To the target organ
  • To the target cell
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7
Q

What are the two major hormones produced in the posterior pituitary gland?

What does each of them do?

A

Vasopressin (anti-diuretic hormone ADH)

  • 􏰀increases collecting duct permeability
  • decreases urine volume (water retention)

Oxytocin

  • Causes milk ejection from the breast (contraction of the myoepithelium)
  • Contraction of the myometrium in the uterus for birthing
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8
Q

Describe the synthesis, storage, and release of posterior pituitary hormones

A
  1. The hormone is made and packaged in cell body of neuron in specific cells of the hypothalamus
  2. These travel down the axon of the neurons into the posterior pituitary
  3. The hormone is stored in vesicles in the posterior pituitary
  4. A signal for release is recieved from the neuron causing release of the hormone into the blood stream to act on distant target organs/cells
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9
Q

Higher centres impact on the neuroendocrine and endocrine relationsips.

What are the main neurons of the hypothalamus synthesising and influencing the posterior pituitary gland?

A

Supraoptic and paraventricular nuclei are responsible for regulating the posterior pituitary hormones

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10
Q

What are the main neurons of the hypothalamus synthesising and influencing the anterior pituitary gland?

A

Arcuate nuclei and other nuclei

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11
Q

How does information from the hypothalamus reach the anterior pituitary gland?

A

Through the hypothalamic‐hypophyseal portal system

= a vascular system

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12
Q

What are the major hormones being produced by the anterior pituitary gland?

Briefly describe each one [7]

A
  1. Adrenocorticotrophic hormone (ACTH/corticotropin)
    • ​Stimulates the adrenal gland to produce a hormone called cortisol. ACTH is also known as corticotrophin.
  2. Thyroid-stimulating hormone (TSH)
    • ​Stimulates the thyroid gland to secrete its own hormone, which is called thyroxine. TSH is also known as thyrotrophin
  3. Luteinising hormone (LH)
    • ​Controls reproductive functioning and sexual characteristics. Stimulates the ovaries to produce oestrogen and progesterone and the testes to produce testosterone and sperm.
  4. Follicle-stimulating hormone (FSH)
    • ​Same as LH
  5. Prolactin (PRL)
    • ​Stimulates the breasts to produce milk. This hormone is secreted in large amounts during pregnancy and breast feeding, but is present at all times in both men and women.
  6. Growth hormone (GH)
    • ​Stimulates growth and repair in all cells of the body.
  7. Melanocyte-stimulating hormone (MSH)
    • ​Exact role in humans is unknown.
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13
Q

Describe the signaling of hormones through the hypothalamic-pituitary portal system

A
  • Neurons in the hypothalamus (arcuate and others) synthesis trophic hormones and release them into the capillaries of the portal system
  • Trophic hormones travel through the portal system to the anterior pituitary gland
  • The different trophic hormones target specific cells in the anterior pituitary gland
  • Endocrine cells of the pituitary respond and release their hormones into the second set of capillaries for distribution to the rest of the body.
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14
Q

What kind of disturbance will happen if there is disruption at the level of the hypothalamus or pituitary

A

Disturbance has potential to cause a wide impact because there are so many trophic and endocrine hormones that are produced and regulated in this region

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15
Q

Fill out the following table

A
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16
Q

Describe Hypothalamic-Pituitary-Adrenal Cortex Axis

A
  • Hypothalamic input to the anterior pituitary: Corticotropin-releasing hormone (CRH)
  • Anterior pituitary releases ACTH (corticotropin)
  • Corticotropin acts on the adrenal cortex
  • The adrenal cortex then releases cortisol
  • Acts on target tissues to cause response
17
Q

Describe the release of growth hormone and insulin-like growth factor

A
  • Hypothalamus produces Growth Hormone Releasing Factor (GHRF) to the anterior pituitary gland
  • The anterior pituitary somatotroph cells release growth hormone into the circulation
  • Growth hormone travels through the liver (the major site of insulin-like growth factor production)
  • ILG-F is released into the blood to act on bone and soft tissue to cause growth
18
Q

Describe the hypothalamic-pituitary-thyroid axis

A
  • The hypothalamus releases thyrotrophin release hormone (TRH) to the anterior pituitary
  • Anterior pituitary releases Thyroid stimulating hormone (TSH) into the bloodstream as a response
  • TSH acts in the thyroid gland which produces T3 and T4
  • T3 and T4 act in the blood stream to regulate metabolic rate
19
Q

Describe the production of LH and FSH

A
  • The hypothalmus produces Gonadotrophin-releasing hormone (GnRH)
  • This acts in the gonadotroph cells of the anterior pituitary to cause release of Leutinising hormone and follicle stimulating hormone
  • They travel through the blood stream to act on the gonads (male testes and female ovaries)
20
Q

What is Kallmann syndrome?

A
  • Embryologically GnRH (gonadotrophin-releasing hormone) neurons failed to migrate via olfactory pathway

= Hypogonadotropic hypogonadism

= Hyposmiaoranosmia (loss of smell)

21
Q

What are the three major means of regulation of hormone pathways?

A
  1. Simple negative feedback (short and long loops)
  2. Neural input
  3. Higher centres
22
Q

How is growth achieved in tissues? [3]

A
  1. Net synthesis of proteins
  2. Lengthening of long bones
  3. Increase in the size and no. of cells in soft tissues
23
Q

What is the absolute essential requirement for growth?

A

Growth hormone (=somatotropin) is essential

24
Q

What are some other important requirements for successful growth? [4]

A
  1. Genetic determination
  2. Adequate diet and nutrition
  3. No chronic disease or stressful environment
  4. Normal mix of growth‐influencing hormones (thyroid hormone, insulin, sex hormones)
25
Q

What are the [3] major detminants of fetal growth before birth?

What is the link between birth size and adult disease

A
  1. Genetics
  2. Environmental (e.g. drug exposure from the mother)
  3. Nutritional (under‐nourished mother)

Research now shows a relationship between a small birth weight and adult disease and a propensity for CVD, reproductive, metabolic , renal and other physiological issues

26
Q

Describe the two stages of post-natal growth spurts to adolescence

A

Postnatal growth spurt

  • First 2 years, 70% brain growth

Growth from 2 years to adolescence

  • little sex difference in height & weight
  • rate of linear growth declines
27
Q

Describe post-adolescent growth

A
  • lengthening of long bones increases growth
  • genetic and hormonal factors: testosterone and estrogen
  • full adult height reached at end of adolescence
28
Q

Describe the three stages of growth hormone development and which structure produces them and what each is responsible for

A
  1. Hypothalamus produces somatostatin and this is Growth hormone inhibiting
  2. The anterior pituitary produces somatotropin (growth hormone)
  3. The liver produces somatomedin (which is insulin like growth factor)
29
Q

What are the major effects [3] of somatotropin (growth hormone)

A

Metabolic effects

  • inreases blood fatty acid and glucose (anti insulin)
  • during prolonged fasting or when body’s energy needs exceeded it is important

Soft tissues and skeleton

  • hyperplasia and hypertrophy on soft tissues & skeleton
  • Increases protein synthesis

Increases IGFs from liver

  • Whole body effects
30
Q

Complete the following table

A
31
Q

What are the somatomedins?

A

Somatomedins = insulin‐like growth factors (IGF‐I and IGF‐II) = polypeptide growth factor

  • The sythesis is stimulated by growth hormone (GH does not directly act on target tissues)
  • Synthesised by the liver & paracrine
32
Q

What is a major requirement for the synthesis of growth hormone (initiation of the synthesis pathway)

A

Normal rhythm of hormones are required for growth:

  • Circadian rhythm
  • Stress and cortisol
  • Fasting
33
Q

Draw the pathway of growth factor production (and the regulating factors)

A
34
Q

Describe the major regulator in the production of growth factor

A
  • The balance between Somatostatin and GHRH will determine whether GH is produced
  • Negative feedback loops (short from the anterior pituitary and long from the liver)
35
Q

What are the requirements for tissue and bone growth [5]

A

Tissue growth requires hormones & paracrine factors

  • GH and IGFs required for protein and cell division
  • Thyroid hormone plays permissive role
  • Insulin supports tissue growth
  • Estrogen close epiphyseal plates of long bones
  • Bone growth requires calcium
36
Q

What kind of pathologies would be seen if there was a growth hormone deficiency?

A
  • Dwarfism due to lack of GH as child
  • Laron dwarfism due to growth hormone insensitivity, GH receptors unresponsive; but they have normal GH
  • Adult onset of GH deficincy shows few effects

Genetically engineered human GH used clinically if GH deficient

37
Q

Abnormal growth can also occur as a result of growth hormone independent causes

A
  • Cretinism
    • childhood hypothyroidism
  • Precocious / early puberty
  • Gonadal dysgenesis
    • XO chromosomes
  • Constitutional delayed / stunted growth
  • Psychosocial dwarfism
    • chronic abuse or neglect
  • Achondroplasia
    • Most common form of dwarfism in humans
    • fibroplast growth factor receptor 3 mutation (cartilage & brain)
38
Q

What are 2 pathologies associated with growth hormone excess

A

Gigantism
• overproduction GH as a child before puberty

Acromegaly
• overproduction GH in adult; bone and soft tissue deformities; increased visera size & protein content
• Progression of acromegaly in one woman

07. Endocrine (10 decks)

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