An Introduction to Neuroendocrinology

Question 1

What is Neuroendocrinology?

Answer 1

• Part of endocrinology involving brain and nerves

* Mostly about hypothalamus and pituitary gland

Question 2

What is endocrinology?

Answer 2

• science of hormones and all the glands and cells that release them
• This includes gonads and prostate, thyroid gland, adrenal glands, pineal gland, pancreas and so on.
• Every single organ is influenced by hormones

Question 3

Definition: Hormones

Answer 3

• any member of a class of signaling molecules in multicellular organisms
• long-distance messenger regulating physiology and behavior

*the same substance may be either neurotransmitter or hormone, depending on the mode of release

(*neurotransmitters are short-term messengers, and tissue-factors in-between)

Question 4

What are the properties of hormones?

Answer 4

• produced by dedicated endocrine cells
• released into the bloodstream
• effectuates functional and/or structural changes in a target cell after receptor binding

Question 5

Name hormones by their chemical composition!

Answer 5

amino acids, peptides, steroids and eicosanoids

Question 6

What are the properties of steroids? (4)

Answer 6

• enzymatic derivates of cholesterol
• steroid hormones are lipophilic (no polarity) and pass through the cellular membrane
• not transcribed from DNA
• steroid receptors are rare in CNS and scattered throughout the cortex

Question 7

AIS

Answer 7

• androgen insensitivity syndrome = “testicular feminization”
• mutations of testosterone receptors, resulting in XY genotype with female phenotype

Question 8

Androgenes and Estrogenes

Answer 8

• level of embryonic androgens (e.g. testosterone) and estrogens (e.g. estradiol) control the expression of male or female phenotypes
• androgens also produced by adrenal glands
• both androgens and estrogens present in all individuals, yet at differing concentrations

Question 9

What are the functions of the hypothalamus?

Answer 9

• integration of information from forebrain, brainstem, spinal cord, and intrinsic chemosensitive neurons
• maintaining homeostasis: comparing input with biological set points and activating adjusting responses
• also involved in…
• control of blood flow
• regulation of energy metabolism
• reproductive activity
• responses to threat

Question 10

Characteristics of hypothalamus?

Answer 10

• floor and ventral wall of the third ventricle
• consists of at least 14 nuclei
• grouping along sagittal axis: anterior (= preoptic) – tuberal – posterior regions
• grouping along medio-lateral axis: periventricular – medial – lateral groups

Question 11

Posterior Pituitary Gland (location and function)

Answer 11

• extension (axons) of neurons in supraoptic and paraventricular nuclei (medial-tuberal region) (or short: extension of hypothalamus)
• releases oxytocin and vasopressin into bloodstream

Question 12

What is the Anterior Pituitary Gland?

+ example of hormones it secretes!

Answer 12

• completely distinct embryologic origin than posterior pituitary
• migrates to fuse with the posterior pituitary during pre-natal development

*it releases e.g. LH & FSH in response to gonadotropin-releasing hormone, GnR (hypothalamic releasing/inhibiting factor)

Question 13

Which hormones stimulate the gonads and what do they induce?

Answer 13

Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) induce…

• formation of oocytes and sperm
• the level of sex hormones

Question 14

Which hormones stimulate the mammillary gland and what do they induce?

Answer 14

• prolactin induces milk-production

* oxytocin induces milk ejection

Question 15

Which hormones stimulate the adrenal glands and what do they induce?

Answer 15

Adreno-corticotrope hormone (ACTH) induces…

• release of cortisol (stress response and nutrient balance)
• release of aldosterone (fluid balance via kidneys)

Question 16

Which hormones stimulate the thyroid gland and what do they induce?

Answer 16

Thyroid-stimulating hormone (TSH) induces…

• release of thyroid hormones thyroxine (T4)
• release of triiodothyronine (T3)

…setting overall metabolism rates

Question 17

What is GH?

Answer 17

Growth Hormone, controls increase of body size during childhood.

Question 18

Tumors of the pituitary gland may…

Answer 18

• …cause growth that can compromise surrounding structures, e.g. the optic chiasm (partial blindness)
• …release hormones that can have downstream effects on other organs, e.g. renewed growth (GH), milk production in both females and males (prolactin), or hyperthyroidism (TSH)

Question 19

Loss of pituitary gland can cause…

Answer 19

amenorrhea, infertility, loss of thermoregulation

Question 20

chronic administration of corticosteroids can lead to…

Answer 20

hyperglycemia, elevated blood pressure, weight increase (e.g. in rheumatic diseases)

Question 21

Cause of “essential” hypertension?

Answer 21

erroneous set- point in hypothalamic blood pressure regulation