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Endocrinology > Pituitary Hormones > Flashcards

Pituitary Hormones Flashcards

1
Q

Anterior pituitary gland

-major hormones it secretes (6)

A
  1. Prolactin (PRL)
  2. Growth hormone (GH)
  3. Adrenocorticotropic hormone (ACTH)
  4. Luteinizing hormone (LH)
  5. Follicle-stimulating hormone (FSH)
  6. Thyroid stimulating hormone (TSH)
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2
Q

Anterior pituitary hormone

  1. stimulators (6)
  2. inhibitors (7)
A
  1. cytokines, ghrelin, GHRH, TRH, GnRH, estrogen

2. glucocorticoids, somatostatin, IGF-1, dopamine, T3, T4, sex steroids

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3
Q

Prolactin (PRL) (2)

A
  • synthesized in lactotrophs
  • lactotroph cell hyperplasia develops during pregnancy and the first few months of lactation
  • the predominant control mechanism is inhibitory –> tonic dopamine mediated suppression of PRL release
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4
Q

Prolactin (PRL)

-when do levels rise (8)

A
  • after exercise
  • meals
  • pregnancy - decline after parturition, but if breast feeding is initiated levels remain elevated
  • sexual intercourse
  • minor surgical procedures
  • general anesthesia
  • chest wall injury
  • acute MI and other forms of acute stress
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5
Q

Prolactin (PRL)

-acts to induce and (3)

A
  • maintain lactation
  • decrease reproductive function –> by suppressing hypothalamic gonadotropin-releasing hormone (GnRH) and pituitary gonadotropin secretion –> impaired gonadal steroidogenesis
  • suppress sexual drive
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6
Q

Growth hormone (6)

A
  • GH-releasing hormone (GHRH) stimulates GH synthesis and release
  • Somatostatin –> inhibits GH secretion
  • IGF-1 –> feeds back to inhibit GH
  • GH secretory rates decline markedly with age
  • secretion is pulsatile –> highest peak levels occurring at night
  • liver and cartilage express the greatest number of GH receptors
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7
Q

Growth hormone

-actions (3)

A
  • GH induces protein synthesis and nitrogen retention and also impairs glucose tolerance by antagonizing insulin action
  • GH stimulates lipolysis –> increased circulating fatty acids levels and enhanced lean body mass
  • GH promotes sodium, potassium and water retention
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8
Q

Growth hormone

-is a single random measurement enough? (2)

A
  • single random GH measurements do not distinguish patients with adult GH deficiency or excess from normal persons
  • secretion is pulsatile –> highest levels at night
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9
Q

Adrenocorticotropic hormone (ACTH) (3)

A
  • secretion is pulsatile and exhibits a characteristic circadian rhythm, peaking about 6AM and reaching the lowest point about midnight
  • CRH is the predominant stimulator of ACTH synthesis and release
  • the major function of the HPA axis is to maintain metabolic homeostasis and mediate the neuroendocrine stress response
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10
Q 
Adrenocorticotropic hormone (ACTH)
-increased by...? (4)
A
  • physiological and psychological stress
  • exercise
  • acute illness
  • insulin-induced hypoglycemia
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11
Q

Thyroid stimulating hormone (TSH) (2)

A
  • TRH is a hypothalamic tripeptide that stimulates TSH synthesis and secretion
  • it also stimulates the lactotroph cell to secrete PRL
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12
Q

Thyroid stimulating hormone (TSH)

-regulation (2)

A
  • TSH secretion is stimulated by TRH, whereas thyroid hormones, dopamine, somatostatin and glucocorticoids suppress TSH by overriding TRH induction
  • Thyrotrope cell proliferation and TSH secretion are both induced when negative feedback inhibition by thyroid hormones is removed (ex: primary hypothyroidism)
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13
Q

Gonadotropins: FSH and LH (4)

A
  • hypothalamic GnRH –> regulates the synthesis and secretion of both LH and FSH
  • estrogens –> modulate gonadotropin secretion
  • chronic estrogen exposure –> inhibitory
  • rising estrogen levels –> positive feedback –> increase gonadotropin pulse frequency and amplitude
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14
Q

Function of FSH and LH

  1. in women
  2. in men
A
  1. FSH regulates ovarian follicle development and stimulates ovarian estrogen production. LH mediates ovulation and maintenance of the corpus luteum
  2. LH induces Leydig cell testosterone synthesis and secretion and FSH stimulates seminiferous tubule development and regulates spermatogenesis
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15
Q

Hypopituitarism

A

-reduction or absolute absence of hormones secretion of anterior, posterior or both parts of pituitary gland

total > panhypopituitarism
partial >2 or more hormones
selective > 1 single hormone

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16
Q
  1. Primary Hypopituitarism
  2. Secondary Hypopituitarism
  3. Acquired Hypopituitarism
  4. Congenital Hypopituitarism
A
  1. disorders of the pituitary gland - loss, damage or dysfunction of cells
  2. disorders of hypothalamus or pituitary stalk - interruption of the nerve or vascular connections to the pituitary gland
  3. commonly during adult life - neoplastic, vascular, traumatic, autoimmune, infectious
  4. disorders present at the birth - rare, usually genetic mutation
17
Q

Hypopituitarism

-Clinical presentation

A
  • space occupying lesion –> hypopituitarism accompanied by headache, visual impairment, change of personality
  • acute onset is rare but life threatening
  • most patient –> slow loss of pituitary function with vague and non-specific symptoms
  • trophic hormone failure occurs sequentially : GH > FSH > LH > TSH > ACTH
  • during childhood –> growth retardation
  • in adults –> hypogonadism
18
Q

Pituitary apoplexy

A
  • bleeding into or impaired blood supply of the pituitary gland.
  • usually occurs in the presence of a tumor

hypopituitarism evident within:

  • several hours –> diabetes insipidus, posterior involvement
  • few days –> adrenal insufficiency, anterior involvement
19
Q

ACTH deficiency

-Clinical features

A

Acute: dizziness, nausea, vomiting, hypotension, hypoglycemia

Chronic: fatigue, weakness, tiredness, pallor, anorexia, weight loss

20
Q

ACTH deficiency

-Lack of adrenal androgens - clinical features

A

Female: loss of sexual desire, loss of pubic and axillary hair

Male: compensation by testosterone from testicles

21
Q

Primary adrenal insufficiency (6)

A
  • Addison’s disease
  • course of the disease: chronic with acute adrenal crisis
  • cortisol deficiency
  • hypoandrogenism
  • aldosterone deficiency
  • hyperpigmentation –> increase ACTH
22
Q

Secondary adrenal insufficiency (5)

A
  • ACTH deficiency due to hypopituitarism
  • course of the disease: chronic with latent onset
  • cortisol deficiency
  • aldosterone is diminished but not abolished
  • hypoandrogenism
23
Q

TSH deficiency

-clinical features

A

-hypothyroidism features

  • tiredness,
  • cold intolerance,
  • constipation,
  • weight gain,
  • hair loss,
  • dry skin,
  • bradycardia,
  • hoarseness,
  • impairment of memory,
  • growth retardation in children
24
Q

FSH/LH deficiency - clinical features in:

  1. Women before menopause
  2. Women during and after menopausal
A
  • loss of target organs (gonads) function
    1. amenorrhea, oligomenorrhea, infertility, loss of libido
    2. osteoporosis, premature atherosclerosis
25
Q

FSH/LH deficiency - clinical features in:

  1. Men
  2. Children before puberty
A
  1. loss of libido, impaired sexual function, decreased muscle and bone mass, erythropoiesis and hair growth
  2. delayed or missing onset of puberty
26
Q

GH deficiency - clinical features:

  1. in children
  2. in adults
A
  1. short stature
  2. decreased muscle mass and strength, fatigue, general weakness and reduced vitality, moderate obesity, hyperlipidemia and decreased HDL, osteopenia, increased risk of metabolic syndrome, increased cardiovascular risks
27
Q

PRL deficiency

-clinical features (2)

A
  • inability to produce milk after childbirth

- isolated hyperprolactinemia is very rare

28
Q

Congenital hypopituitarism

  1. Acquired pituitary failure - cause
  2. Hypothalamic dysfunction
  3. Imp. transcription factors
A
  1. birth trauma, including cranial hemorrhage, asphyxia and breech delivery
  2. dysgenesis of the septum pellucidum or corpus callosum
  3. Pit-1 and Pop-1
29
Q

Autosomal dominant or recessive Pit-1 mutations

A

cause combined GH, PRL and TSH deficiencies

30
Q

Familial and sporadic Pop-1 mutations

A

result in combined GH, PRL, TSH and gonadotropin deficiency

31
Q

Congenital hypopituitarism - Kallmann syndrome (5)

A
  • defective hypothalamic gonadotropin releasing hormone (GnRH) synthesis
  • associated with anosmia or hyposmia due to olfactory bulb agenesis or hypoplasia
  • GnRH deficiency prevents progression through puberty
  • males –> delayed puberty and pronounced hypogonadal features (micropenis), may result of low testosterone levels during pregnancy
  • females –> primary amenorrhea and failure of secondary sexual development
32
Q

Congenital hypopituitarism - Kallmann syndrome

-hormone levels

A
  • low LH and FSH

- low concentration of sex steroids (testosterone and estradiol)

33
Q

Hypopituitarism

-diagnosis - lab investigations

A

-low or inappropriately normal levels of trophic hormones in the setting of low levels of target hormones

34
Q

Hormone replacement therapy

  1. ACTH
  2. TSH
  3. GH
A
  1. Hydrocortisone (1-20mg AM; 5-10 mg PM), Cortisone acetate, Prednisone (5mg AM)
  2. L-thyroxine
  3. Somatotropin
35
Q

Hormone replacement therapy

-FSH/LH

A

Males
-Testosterone enanthate (200mg IM every 2 weeks) or Testosterone skin patch

Females

  • Conjugated estrogen (0.65-1.25 mg for 25 days) and Progesterone (5-10 mg qd) on days 16-25
  • Only estrogen –> possible complications: proliferation of mucous membrane of uterus, if there is no progesterone we won’t have menstrual cycle and then there is increased risk of cancer

Endocrinology (11 decks)

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