7.4: The Pituitary Gland
- Page ID
- 191394
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)What Is the Pituitary Gland?
The pituitary gland is the master gland of the endocrine system, the system of glands that secrete hormones into the bloodstream (Figure \(\PageIndex{1}\)).
The pituitary gland is considered the master gland of the endocrine system because it controls the rest of the endocrine system. Many pituitary hormones either promote or inhibit the secretion of hormones from other endocrine glands.
Structure and Function of the Pituitary Gland
The size of a pea, the pituitary gland protrudes from the bottom of the hypothalamus at the base of the inner brain via a thin stalk (called the infundibulum) (Figure \(\PageIndex{2}\)).
Blood vessels and nerves in the stalk allow direct connections between the hypothalamus and the pituitary gland. The pituitary gland consists of two bulb-like lobes: an anterior lobe and a posterior lobe.
Anterior Lobe of the Pituitary
The anterior pituitary is at the front of the pituitary gland. It synthesizes and secretes hormones into the blood and is regulated primarily by hypothalamic hormones (Table \(\PageIndex{1}\)).
| Hormone | Target | Effect(s) |
|---|---|---|
| Adrenocorticotropic hormone (ACTH) | Adrenal glands | Stimulates the cortex of each adrenal gland to secrete its hormones |
| Thyroid-stimulating hormone (TSH) | Thyroid gland | Stimulates the thyroid gland to secrete thyroid hormone |
| Growth hormone (GH) | Body cells | Stimulates body cells to synthesize proteins and grow |
| Follicle-stimulating hormone (FSH) | Ovaries, testes | Stimulates the ovaries to develop mature eggs; stimulates the testes to produce sperm |
| Luteinizing hormone (LH) | Ovaries, testes | Stimulates the ovaries and testes to secrete sex hormones; stimulates the ovaries to release eggs |
| Prolactin (PRL) | Mammary glands | Stimulates the mammary glands to produce milk |
The hypothalamus secretes releasing and inhibiting hormones that travel through capillaries directly to the anterior lobe of the pituitary gland.
The hormones stimulate the anterior pituitary to either release or stop releasing particular pituitary hormones (Table \(\PageIndex{2}\)).
| Hypothalamic Hormone | Effect on Anterior Pituitary |
|---|---|
| Thyrotropin-releasing hormone (TRH) | Release of thyroid-stimulating hormone (TSH) |
| Corticotropin-releasing hormone (CRH) | Release of adrenocorticotropic hormone (ACTH) |
| Gonadotropin-releasing hormone (GnRH) | Release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) |
| Growth hormone-releasing hormone (GHRH) | Release of growth hormone (GH) |
| Growth hormone inhibiting hormone (GHIH) (Somatostatin) | Stopping of growth hormone release |
| Prolactin-releasing hormone (PRH) | Release of prolactin |
| Prolactin inhibiting hormone (PIH) (Dopamine) | Stopping of prolactin release |
Posterior Lobe of the Pituitary
The posterior pituitary is at the back of the pituitary gland. This lobe does not synthesize any hormones but stores them from the hypothalamus along the axons of nerves connecting the two structures (Figure \(\PageIndex{2}\)).
The posterior pituitary then secretes those stored hormones into the bloodstream as needed.
Hypothalamic hormones secreted by the posterior pituitary include vasopressin and oxytocin.
- Vasopressin (also called antidiuretic hormone, or ADH) helps to maintain homeostasis in body water. It stimulates the kidneys to conserve water by producing more concentrated urine. Specifically, vasopressin targets the renal (kidney) ducts and increases their permeability to water. This allows more water to be resorbed by the body rather than excreted in the urine.
- Oxytocin (OXY) has a number of different functions, including:
- stimulating uterine contractions during childbirth.
- stimulating milk letdown in a nursing mother.
- parent-infant bonding
- trust and relationship building
- romantic attachment and sexual arousal