Endocrine Glands

EndocrinologyEndocrinologyEndocrinologyEndocrinology

Salvador Dalí, 1952: Galatea of the spheres

Learning ObjectivesLearning ObjectivesLearning ObjectivesLearning Objectives

To understand what the reproductive To understand what the reproductive endocrine glands and hormones are.endocrine glands and hormones are.

To understand the characteristics To understand the characteristics and functions of these hormones.and functions of these hormones.

To understand how the To understand how the concentrations of these hormones in concentrations of these hormones in the blood are controlled.the blood are controlled.

• What is endocrinology?What is endocrinology?– Study of structure & function of endocrine Study of structure & function of endocrine

glands and the role of their secretions glands and the role of their secretions (hormones)(hormones)

• What is an endocrine gland?What is an endocrine gland?– Organs or groups of cells which produce Organs or groups of cells which produce

hormones and secrete them into the hormones and secrete them into the vasculaturevasculature

• What is a hormone?What is a hormone?– A chemical messenger which travels via the A chemical messenger which travels via the

circulation to reach target organs and circulation to reach target organs and subsequently elicit a specific effectsubsequently elicit a specific effect

Endocrinology ?Endocrinology ?Endocrinology ?Endocrinology ?

Present in Present in circulationcirculation in in lowlow amountsamounts

Inhibit or accelerate reactions in cellsInhibit or accelerate reactions in cells

Are not secreted at constant ratesAre not secreted at constant rates

Require a specific receptorRequire a specific receptor

Characteristics of Characteristics of hormones:hormones:

Characteristics of Characteristics of hormones:hormones:

Require a specific receptorRequire a specific receptor

Characteristics of Characteristics of hormones:hormones:

Characteristics of Characteristics of hormones:hormones:

Modes of TransmissionModes of TransmissionModes of TransmissionModes of Transmission

Endocrine:Endocrine: hormones transported by hormones transported by the blood to act on a distant organ. the blood to act on a distant organ. (classical definition)(classical definition)

Neuroendocrine:Neuroendocrine: hybrid; nerve hybrid; nerve secretes its chemical messenger, is secretes its chemical messenger, is taken into a capillary and carried to taken into a capillary and carried to many cells.many cells.

Modes of TransmissionModes of TransmissionModes of TransmissionModes of Transmission

Paracrine:Paracrine: hormones simply diffuse hormones simply diffuse directly to neighboring target cells, directly to neighboring target cells, by-passing the circulatory system.by-passing the circulatory system.

Autocrine:Autocrine: a given cell may respond to a given cell may respond to its own hormone secretion.its own hormone secretion.

Locations of Some Locations of Some Endocrine GlandsEndocrine GlandsLocations of Some Locations of Some Endocrine GlandsEndocrine Glands

Classes of Hormones: Classes of Hormones: ProteinsProteins

Classes of Hormones: Classes of Hormones: ProteinsProteins

Classes of Hormones: Classes of Hormones: SteroidsSteroids

Classes of Hormones: Classes of Hormones: SteroidsSteroids

Classes of Hormones: Classes of Hormones: ProstaglandinsProstaglandins

Classes of Hormones: Classes of Hormones: ProstaglandinsProstaglandins

Hypothalamus

Pituitary Gland

Reproductive HormonesReproductive HormonesReproductive HormonesReproductive HormonesHormoneHormone StructurStructur

e e OriginOrigin TargetTarget TargetTarget FunctionFunction

Gonadotropin Releasing Hormone (GnRH)

Decapeptide Hypothalamus Anterior PituitaryAnterior Pituitary

1. Stimulates the release of LH and FSH

Oxytocin

Octapeptide

Hypothalamus (Synthesized)

Posterior Pituitary

(Stored)

Smooth muscle of the epidydimal tail, vas deferens, and

ampulla

myometrium,

endometrium,

and mammary gland

1. Stimulates PGF2α synthesis

2. muscle contraction

Follicle Stimulating Hormone

(FSH)Glycoprotein Anterior Pituitary

testis

(sertoli cells)

ovaries

(granulosa cells)

1. Sertoli cell function

2. Spermatogenesis

1. Follicular development

2. Estradiol synthesis

Luteinizing Hormone

(LH)

Glycoprotein Anterior Pituitarytestis

(leydig cells)

ovaries

(thecal cells & luteal cells)

1. Stimulates testosterone

production

1. Stimulates ovulation

2. Induces formation of the

CL as well as

progesterone secretion

Reproductive HormonesReproductive HormonesReproductive HormonesReproductive HormonesHormoneHormone StructurStructur

e e OriginOrigin TargetTarget TargetTarget FunctionFunction

Prolactin Glycoprotein Anterior Pituitary Testis and Brain Mammary Gland

1. Stimulates milk production

2. Maternal behavior

1. Maternal behavior

Progesterone

(P4)Steroid

Corpus luteum and

Placenta* *(species specific)

-

Endometrium & myometrium,

hypothalamus, and mammary

gland

1. Maintenance of pregnancy

2. Inhibit GnRH release

3. Mammary growth and

secretion

Estradiol

(E2)Steroid

Sertoli cells

Granulosa Cells

Brain

Hypothalamus & pituitary, entire reproductive

tract, and brain

1. Regulate GnRH, LH & FSH

2. Increased secretory activity to enhance uterine motility

3. Sexual behavior (heat)

1. Sexual behavior

Testosterone

(T)Steroid

Leydig cells

Theca interna cells

Sertoli cells, accessory sex glands, brain, and skeletal

muscle

Granulosa cells, brain, and

skeletal muscle

1. Spermatogenesis

2. Promotes secretion of accessory glands

3. Secondary sex characteristics

1. Estradiol synthesis