Pituitary Gland Flashcards

Flashcards covering the key concepts of the pituitary gland, its hormones, and their functions, based on provided lecture notes.

Where is the pituitary gland located?

A pocket of the sphenoid bone at the base of the brain, closely related to the hypothalamus.

What hormones are secreted by the anterior lobe of the pituitary gland?

Thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin, and growth hormone.

What target organ does prolactin act on?

The breast.

What do tropic hormones do?

They stimulate secretion of hormonally active substances by other endocrine glands or, in the case of growth hormone, the liver and other tissues.

What hormones are stored in the posterior lobe of the pituitary?

Oxytocin and vasopressin.

What does the posterior lobe of the pituitary consist of predominantly?

Nerves that have their cell bodies in the hypothalamus.

What does this chapter focus predominantly on?

Growth hormone and facilitating the activity of other hormones, along with a number of general considerations about the pituitary.

What does the posterior pituitary arise as?

An extension of the hypothalamus.

What does the anterior pituitary arise as embryologically?

An invagination of the pharynx (Rathke pouch).

What are the five types of secretory cells identified in the anterior pituitary?

Somatotropes, lactotropes, corticotropes, thyrotropes, and gonadotropes.

What hormone do somatotropes secrete?

Growth hormone.

What hormone do lactotropes secrete?

Prolactin.

What hormone do corticotropes secrete?

ACTH.

What hormone do thyrotropes secrete?

TSH.

What hormone do gonadotropes secrete?

FSH and LH.

What do paracrine factors produced by folliculostellate cells do?

Regulate the growth and function of the secretory cells.

What cells synthesize a large precursor protein that is cleaved to form a family of hormones?

Corticotropes of the anterior lobe (or intermediate lobe cells, when present).

What is POMC hydrolyzed to in Corticotropes?

ACTH and β-lipotropin (β-LPH), plus a small amount of β-endorphin.

What is POMC hydrolyzed to in Intermediate lobe cells?

Corticotropin-like intermediate-lobe peptide (CLIP), γ- LPH, and appreciable quantities of β-endorphin.

How do Fish, reptiles, and amphibia change the color of their skin?

moving black or brown granules into or out of the periphery of pigment cells called melanophores.

What are the granules in melanophores made up of?

Melanins, which are synthesized from dopamine and dopaquinone.

What do mammals have that have multiple processes containing melanin granules?

Melanocytes.

What is a hallmark of hypopituitarism related to pigmentation?

Abnormal pallor.

What causes hyperpigmentation?

Adrenal insufficiency due to primary adrenal disease.

What are albinos characterized by?

A congenital inability to synthesize melanin resulting from a variety of different genetic defects in the pathways for melanin synthesis.

What is Piebaldism characterized by?

Patches of skin that lack melanin as a result of congenital defects in the migration of pigment cell precursors from the neural crest during embryonic development.

What does Vitiligo involve?

A similar patchy loss of melanin, but the loss develops progressively after birth secondary to an autoimmune process that targets melanocytes.

What does the hGH-N gene code for?

One, hGH-N, codes for the most abundant (“normal”) form of growth hormone.

hGH-V and hCS are primarily products of what?

hGH-V and hCS are primarily products of the placenta

How is the plasma protein that a portion of circulating growth hormone is bound to produced?

It appears to be produced by cleavage of receptors in humans, and its concentration is an index of the number of growth hormone receptors in the tissues.

Where is growth hormone metabolized?

The liver.

What does the hypothalamus secrete to controls growth hormone production?

Growth hormone–releasing hormone (GHRH) as well as somatostatin, which inhibits growth hormone release.

What is a third regulator of growth hormone secretion?

Ghrelin

What kind of activity does Ghrelin have?

Stimulating activity.

How does growth hormone increase the circulating IGF-1?

Growth hormone also increases circulating IGF-I, and IGF-I in turn exerts a direct inhibitory action on growth hormone secretion from the pituitary.

What conditions increase growth hormone secretion?

Hypoglycemia and/or fasting.

What decreases growth hormone secretion?

REM sleep.

How does growth hormone bind to its receptor?

Growth hormone has two domains that can bind to its receptor, and when it binds to one receptor, the second binding site attracts another, producing a homodimer

What is essential for receptor activation?

Dimerization.

What does Growth hormone activate?

Activates many different intracellular signaling cascades

Whats a particular note of intracellular signaling cascade?

The JAK2–STAT pathway

How is stature increased?

Chondrogenesis is accelerated, and as the cartilaginous epiphysial plates widen, they lay down more bone matrix at the ends of long bones.

When the epiphyses are closed, what does an overabundance of growth hormone produces?

Acromegaly.

What kind of hormone is Growth hormone?

A protein anabolic hormone and produces a positive nitrogen and phosphorus balance, a rise in plasma phosphorus, and a fall in blood urea nitrogen and amino acid levels.

What causes gigantism in children and acromegaly in adults?

Tumors of the somatotropes of the anterior pituitary (pituitary adenomas)

What is the mainstay of therapy for acromegaly?

Somatostatin analogues that inhibit the secretion of growth hormone.

What are At least some forms of growth hormone?

Diabetogenic.

What does Growth hormone increases the ability of?

The pancreas to respond to insulinogenic stimuli such as arginine and glucose.

The effects of growth hormone on growth, cartilage, and protein metabolism depend on what?

Somatomedins, which are polypeptide growth factors secreted by the liver and other tissues.

What are humans probably the only circulating somatomedins?

Insulin-like growth factor I (IGF-I, somatomedin C) and IGF-II

What is Secretion of IGF-I stimulated by?

Growth hormone after birth, and it has pronounced growth-stimulating activity.

how secretion of IGF-I is independent

Independent of growth hormone before birth but is stimulated by growth hormone after birth, and it has pronounced growth-stimulating activity.

How is IGF-II independent?

Independent of growth hormone and plays a role in the growth of the fetus before birth.

It was originally thought to produce growth by a direct action on tissues, and then later was believed to act solely through its ability to induce what?

Growth hormone, and then later was believed to act solely through its ability to induce somatomedins.

What does growth depend on?

adequate nutrition.

What is the most important extrinsic factor affecting growth?

The food supply.

What is the second growth spurt, at the time of puberty, is due to?

Thyroid hormones, androgens, and estrogens.

What is the Eventual cessation of growth is due to?

Closure of the epiphyses in the long bones by estrogens

What spikes are larger, especially during puberty, so the mean plasma level over 24 h is increased?

HGH

What hormones The contributions of hormones to growth after birth are shown diagrammatically ?

thyroid hormones.

What is The growth spurt that occurs at the time of puberty due to

To the secretion of adrenal androgens at this time in both sexes and the protein anabolic effect of these androgens; however, it is also due to an interaction among sex steroids, growth hormone, and IGF-I.

What do Estrogens ultimately terminate growth by causing

Estrogens ultimately terminate growth by causing the epiphyses to fuse to the long bones

how growth increased by thyroid homes ?

potentiated by thyroid hormones, which by themselves have no effect on growth.

What happens Following illness or starvation in children?

Catch-up growth takes place during which the growth rate is greater than normal.

What cause loss-of-function mutations

The FSH receptor

what is the cause for Gain-of-function mutations

Ovarian hyperstimulation syndrome

childhood abuse and neglect can also cause dwarfism, This condition is known as what?

Kaspar Hauser syndrome

achondroplasia most common form of dwarfism, condition?

Autosomal dominant

Structurally similar prolactins are secreted?

endometrium and by the placenta.

what regulatory factors ?

The regulatory factors for prolactin secretion by the pituitary overlap, in part, with those causing secretion of growth hormone

What overlaps factors for prolactin secretion

The regulatory factors for prolactin secretion by the pituitary overlap, in part, with those causing secretion of growth hormone

what prolactin in secretion

Facilitates the secretion of dopamine in the median eminence

The receptors for FSH and LH ?

are G-protein-coupled receptors coupled to adenylyl cyclase through a stimulatory G-protein (Gs; see Chapter 2).

The human prolactin receptor what ?

resembles the growth hormone receptor and is one of the superfamily of receptors that includes the growth hormone receptor and receptors for many cytokines and hematopoietic growth factors

what FSH do ?

is responsible for the early growth of ovarian follicles in the female

What LH responsible ?

Is responsible for ovulation, the initial formation of the corpus luteum, and secretion of progesterone.