Endocrine Hypothalamus

1. Thirst Center

2. Feeding Centers

3. Control of Reproductive Behavior -> Steroid hormones (estrogen, progesterone, TST)

4. Regulation of temperature-- Thermostat

5. Control of Biological Rhythm

6. Regulates Secretory activity of Pituitary gland

Endocrine Hypothalamus Functions

• Basal part of the diencephalon lying between the thalamus

• Forms the wall and lower part of the ventricle of the brain

Anatomical Boundaries of Endocrine Hypothalamus

1 Median eminence

2 Hypophyseal Portal System (hypothalamohypophyseal portal system)

Vascular Connections of Endocrine Hypothalamus

Median eminence

Vascular connections that is the *lower part tuber cinereum* which is richly supplied with blood vessels that *drain in the pituitary stalk*

Hypophyseal Portal System (hypothalamohypophyseal portal system)

Vascular connections that is the Vascular link between the *median eminence* and the *pituitary gland*

1 Hypothalamic nuclei

2 Supraoptic nuclei (SON) & Paraventricular nuclei (PVN)

3 Supraopticoparaventricularhypophysial tract

Neural connections of Endocrine Hypothalamus

Hypothalamic nuclei

clusters of neurons

Supraoptic nuclei (SON) and Paraventricular nuclei (PVN)

Composed of cell bodies whose axons extend into the median eminence and then into the neurohypophysis

Supraopticoparaventricularhypophysial tract

A nerve tract composed of the axons of the SON and PVN

1. Thyrotropin Releasing Hormone (TRH)

2. Growth Hormone-Release Inhibiting Hormone (GH-RIH)/Somatostatin (Somatotropin Release-Inhibiting Hormone)

3. Somatocrinin (Growth Hormone-Releasing Hormone)/Somatotropin Releasing Hormone (STH-RH)

4. Gonadotropin-releasing Hormone (GnRH)/Luteinizing HormoneReleasing Hormone (LHRH)

5. Corticotropin Releasing Hormone (CRH)

6. Prolactin Release-Inhibiting Factor (PIF)/Dopamine

7.Prolactin-releasing Factor/Hormone (PRF/H)

8.MSH Release-Inhibiting Hormone (MSH-RIH)

Hypothalamic Releasing Hormones /Hypophysiotropic Hormones (8)

-Thyroid stimulating hormone (TSH)

-PRL

*Thyrotropin Releasing Hormone (TRH)* Functions

-Stimulates the *Anterior Pituitary* to release __

-Stimulates the release of ____in humans (persons with acromegaly and chronic renal insufficiency), cattle, sheep and rats

Growth Hormone-Release Inhibiting Hormone (GH-RIH)/Somatostatin (Somatotropin Release-Inhibiting Hormone)

-Also secreted by *pancreatic delta cells*, *GIT mucosa cells* (clear cells of thyroid gland) and *Hypothalamus*

- Function: *Inhibit the secretion of Growth Hormone* by the anterior pituitary gland

-pancreatic delta cells

-GIT mucosa cells

-hypothalamus

Somatostatin is secreted by

Growth Hormone (GH)

*Somatostatin's* function is to inhibit ___

Somatocrinin (Growth Hormone-Releasing Hormone)/Somatotropin Releasing Hormone (STH-RH)

Function: Stimulate the secretion of GH by the somatotropes in the anterior pituitary gland

Gonadotropin-releasing Hormone (GnRH)/Luteinizing HormoneReleasing Hormone (LHRH)

Function: Stimulate the release of FSH and LH by the anterior pituitary (Gonadotropes secretory cells of FSH and LH)

Corticotropin Releasing Hormone (CRH)

Function: Stimulate the release of ACTH by the anterior pituitary gland (Corticotropes - cells responsible for the secretion of ACTH)

Prolactin Release-Inhibiting Factor (PIF)/Dopamine

Function: Inhibits prolactin release from the anterior pituitary gland

Prolactin-releasing Factor/Hormone (PRF/H)

Function: Synonymous to TRH -> presence of TRH would also mean a release of PRH

MSH Release-Inhibiting Hormone (MSH-RIH)

Function : Under inhibitory control of hypothalamus

Hypophysis Cerebri

Pituitary Gland is also called

Hypothalamic-Pituitary Relationship

• Intimately related morphologically and functionally

• Where nervous and endocrine systems interact

anterior pituitary

Hypothalamus regulates secretions of

hypothalamus

Posterior pituitary is an extension of the

1 body function

2 secretion of other endocrine glands

Anterior pituitary produces nine major hormones that regulates: (2)

hypothalamic-Hypophysial portal system

Anterior lobe of the Pituitary gland is linked to the hypothalamus via the

Hypothalamic-Hypophysial Portal system

*Anterior lobe of the Pituitary gland* is linked to the *hypothalamus* via this area. Thus, blood from the hypothalamus containing *hypothalamic hormones* is delivered directly and in high concentrations to the anterior pituitary.

neural tissue

Posterior lobe of the pituitary gland is derived from the ____. The nerve cell bodies are located in the hypothalamic nuclei. Hormones secreted are synthesized in the hypothalamus, packaged in secretory granules, and transported down the axons to be stored for release by the posterior lobe.

hypothalamic nuclei

nerve cell bodies are located in the

-hypothalamus

-secretory granules

-axons

-posterior lobe

*Hormones* secreted are

-synthesized in

-packaged in

-transported down the ___

-to be stored by release by

roof of the mouth

Anterior Pituitary Gland develops from the

Rathke's pouch

Inward invagination of the oral ectoderm of the stomodeum

floor of the brain

Posterior Pituitary Gland develops from

infundibulum

Posterior Pituitary Gland connects to the *hypothalamus* by

1 Adenohypophysis

2 Neurohypophysis

Structure of Pituitary Gland (2)

Anterior Lobe

-Pars distalis

-Pars tuberalis

Intermediate lobe

-Pars intermedia

Adenohypophsis Parts

• Posterior → Pars nervosa

• Infundibulum → Stalk

Neurohypophysis parts

"Master Endocrine Gland"

Pituitary Gland/Hypophysis other name

fishes

Animals whose Pituitary Gland has *NO distinct neural lobe*

Pars intermedia

*Birds* lacks this part of the Pituitary gland

Birds, Elephants, Whales, Adult humans

Animals that *lacks Pars intermedia*

-Corticotropin (ACTH)

-Basophil

If the Cell type is: Corticotroph, what is the

-Hormone

-Staining Characteristics

-Thyrotropin (TSH)

-Basophil

If the Cell type is: Thyrotroph, what is the

-Hormone

-Staining Characteristics

-Follitropin (FSH) & Lutropin

-both Basophil

If the Cell type is: Gonadotroph

a. FSH

b. LH

, what is the

-Hormone

-Staining Characteristics

-Prolactin (PRL)

-Acidophil

If the Cell type is: Lactotroph (mammotroph), what is the

-Hormone

-Staining Characteristics

-Somatotropin (STH)

-Acidophil

If the Cell type is: Somatotroph , what is the

-Hormone

-Staining Characteristics

tropin/tropic hormones

hormones that regulate the hormone secretion of target endocrine tissues

1. Glycoproteins

2. Somatomammotropins

3. Proopiomelanocortin (POMC) family

Tropins/Tropic Hormones (3)

alpha

*Glycoproteins* subunits that are identical

Beta

*Glycoproteins* subunits that confer specificity

1 Thyroid-Stimulating Hormone (TSH, Thyrotropin)

2 Gonadotropin: LH and FSH

Glycoproteins (2)

Thyroid-Stimulating Hormone (TSH, Thyrotropin)

Stimulates TH synthesis and release

Stimulates ovarian function and steroidogenesis

LH & FSH function in Female

Stimulates testicular function and steroidogenesis

LH & FSH function in Male

Somatomammotropins

Single-peptide chain with disulfide bonds

1. Growth Hormone (GH, somatotropin)

2. Prolactin (mammotropin)

Somatomammotropins (2)

Growth Hormone (GH, somatotropin)

Stimulates somatic growth (via IGF-1) and is counter regulatory to insulin

Prolactin (mammotropin)

promotes lactation in females

Proopiomelanocortin (POMC) family

Precursor for small peptides produced by post-translational processing

1. Adrenocorticotropic hormone (ACTH)

2. Melanocyte Stimulating Hormone (MSH)

Proopiomelanocortin (POMC) family (2)

Adrenocorticotropic hormone (ACTH)

Stimulates adrenal growth and steroidogenesis

Melanocyte Stimulating Hormone (MSH)

Skin darkening in lower animals and at high concentrations in humans physiologic roles not established

Corticotropin-releasing hormone (CRH)

Hypophysiotropic Hormones whose action is to *Stimulates POMC synthesis and ACTH secretion*

Gonadotropin releasing hormone (GnRH)

Hypophysiotropic Hormones whose action is to *Stimulates FSH and LH secretion*

Growth Hormone releasing Hormone (GHRH)

Hypophysiotropic Hormones whose action is to *Stimulates GH release*

Somatostatin (Somatotropin Release-Inhibiting Factor, SRIF)

Hypophysiotropic Hormones whose action is to *Inhibits GH secretion*

Prolactin-stimulating factor

Hypophysiotropic Hormones whose action is *unknown*

Prolactin-inhibiting factor (dopamine)

Hypophysiotropic Hormones whose action is *Inhibits the release of prolactin*

Thyroid releasing Hormone (TRH)

Hypophysiotropic Hormones whose action is *Stimulates TSH and PRL secretion*

1. Thyrotropin/Thyroid Stimulating Hormone/TSH

2. Gonadotropin (FSH & LH)

3. Somatotropin (STH, Growth Hormone)

4. Prolactin (PRL)

5. Adrenocorticotropic Hormone (ACTH)/Corticotropin

6. Melanocyte-stimulating hormone (MSH, intermedin/ melanotropin)

7. Beta endorphins

8. Lipotropins

Anterior Pituitary Hormones (9)

Thyrotropin/Thyroid Stimulating Hormone/TSH

• Glycoprotein with α and β subunits (confer biological activity)

• Amino acid composition of the turtle is similar to that of bovine TSH

1 Control of Thyroid Gland Function

2 Maintain size & functional integrity of chief cells of the thyroid gland

3 Control & Regulation of many Biological processes

4 Functional aspects of Thyroid Physiology

5 Endocytosis & Release of TSH

6 Synthesis & Secretion of Thyroid Hormones

Thyrotropin/Thyroid Stimulating Hormone/TSH FUNCTIONS

inducing metamorphosis

*Thyrotropin* function in *amphibians*

important in thermogenesis

*Thyrotropin* function in *mammals*

Endocytosis & release of TSH

Thyrotropin Principal Action

a) Thyrotropin Releasing Hormone (TRH)

b) Thyroid hormones

c) other factors

Regulation of Secretion of Thyrotropin

Thyrotropin Releasing Hormone (TRH)

Regulation of Secretion of Thyrotropin

wherein there is a Constant exposure of thyrotropes to TRH(Negative Feedback Mechanism)

Thyroid hormones

Regulation of Secretion of Thyrotropin

wherein

- Main factor (Negative Feedback Mechanism)

- Increase in circulating thyroid hormones would lead to an increase sensitivity of thyrotropes to TRH and vice versa

-Lower environmental temperature

-Estrogen

-Inhibitory to TSH: Somatostatin (GH); Dopamine; excess Glucocorticoids (GCC)

Other factors of Regulating of Secretion of Thyrotropin (TSH)

Estrogen

increase the sensitivity of thyrotropins to TRH

Somatostatin (GH); Dopamine; Excess GCC

Inhibitory to TSH

Gonadotropin

Glycoprotein whose half life in *sheep* is 2-4 hrs

a) hypothalamic control

b) environmental conditions

Regulation of Secretion of *Gonadotropin*

-Changing season & daylight length

-ie eye to hypothalamus

Environmental conditions that regulates the secretion of *Gonadotropin*

1 Early development of Ovarian Follicle & Estrogen secretion (F)

2 Spermatid Maturation (M)

3 2 fold role in Male

4 Stimulates synthesis of Testicular (Sertoli cell) androgen-binding protein

Follicle Stimulating Hormone (FSH)/Follitropin Functions

1 ^ LH receptor population of testicular Leydig cells (interstitial cells) -> ^ sensitivity to action of LH

2 together w LH to stimulate spermatogenesis

Two-fold role of FSH in the male

Inhibin

inhibits secretion of FSH

Estradiol

estrogen secreted by the ovaries

1 Stimulate interstitial (Leydig cells) to to secrete Testosterone -> secondary sexual characteristics

2 Dependent on the action of FSH to increase the LH receptor in Leydig cells

3 Stimulate Ovarian follicle toward maturation, Estrogen prod., Ovulation

Luteinizing Hormone or Interstitial Cell Stimulating Hormone/Lutropin Functions

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Somatotropin (STH, Growth Hormone)

▪ Complex protein - polypeptide

▪ Have species differences but is species specific i.e. Rat responds to fish ___ and man to monkey ___

-Increases osseus & soft tissues of the body

-Hypertrophy

-Hyperplasia

Growth (linear)/Anabolic Effects of *Somatotropin (STH, Growth Hormone*)

epiphyseal plate closes

Growth of the long bone continues until the

Rats

Animal whose *Epiphyseal plate* DOES NOT close

a) Amino acid - "protein-sparing effect"

b) Increases Nitrogen retention in Body

c) Enhances DNA transcription

d) Enhances MRNA translation

e) Increase in cellular uptake of Amino acid

f) Fatty acid

g) Glucose

Metabolic Effects of *Somatotropin (STH, Growth Hormone)

Increases cell permeability to amino acid

How does Somatotropin increase the build up of muscle mass

somatomedins

*Somatotropins* Increases the *cellular uptake of amino acids* & this is mediated indirectly through the actions of _____ released from the liver in response to STH stimulation of hepatocytes

-Increase Lipolysis

-Mobilize adipose tissue

-Increase fatty acid levels in blood (use for energy)

SOMATOTROPINS effects on *Fatty acids*

-Anti-insulinic effect -"pituitary diabetes"

-Elevates Blood Sugar level stimulating the pancreatic islets to produce insulin

SOMATOTROPINS effects on *Glucose*

Pituitary diabetes (diabetes insipidus)

is a condition characterized by persistent thirst and frequent urination. It occurs due to inadequate secretion of vasopressin or ADH from the posterior part of the pituitary gland