8.5: Pituitary Gland and Hypothalamus
- Page ID
- 121077
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The hypothalamus–pituitary complex acts as the body’s hormonal command center, linking the nervous and endocrine systems to regulate hormone production and maintain homeostasis.
- Describe the structure and function of the hypothalamus–pituitary complex, including how it links the nervous and endocrine systems.
- Compare the anterior and posterior pituitary glands in regards to hormone production, storage, and release, and how each is regulated by the hypothalamus.
The hypothalamus–pituitary complex serves as the command center of the endocrine system. It secretes hormones that either act directly on target tissues or regulate the hormone production of other endocrine glands. This complex also bridges the nervous and endocrine systems, translating neural signals into hormonal messages. In many cases, sensory information processed by the nervous system must pass through the hypothalamus–pituitary complex before it can trigger hormonal responses that maintain homeostasis.
Hypothalamus
The hypothalamus is part of the brain located just below the thalamus. It plays a major role in linking the nervous system and the endocrine system by controlling the pituitary gland. The pituitary hangs below the hypothalamus by a thin stalk called the infundibulum and sits in a small bony cavity of the skull called the sella turcica. The hypothalamus produces several hormones and controls when the pituitary releases its own.
Posterior Pituitary
The posterior pituitary is actually part of the brain, not a true gland. It is made of nerve fibers that come from special neurons in the hypothalamus. These neurons make two hormones: oxytocin and antidiuretic hormone (ADH), also known as vasopressin. The hormones travel down the axons to the posterior pituitary, where they are stored. When the hypothalamus sends the appropriate signal, the posterior pituitary releases these hormones into the bloodstream.
Anterior Pituitary
The anterior pituitary develops from tissue in the roof of the mouth during early growth and later moves toward the brain. Unlike the posterior pituitary, the anterior pituitary makes its own hormones. However, it does not act on its own — it is controlled by the hypothalamus. The hypothalamus sends releasing hormones to tell the anterior pituitary to release hormones, and inhibiting hormones to tell it to stop. These hypothalamic hormones reach the anterior pituitary through a special group of blood vessels called the hypophyseal portal system. This system forms a direct connection between the hypothalamus and the anterior pituitary, allowing hormones to travel quickly and directly without going through the whole bloodstream.
Six hormones are synthesized in the anterior pituitary. These are the growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin. Of the hormones of the anterior pituitary, TSH, ACTH, FSH, and LH are collectively referred to as tropic hormones (trope- = “turning”) because they turn on or off the function of other endocrine glands.
| Pituitary lobe | Associated hormones | Effect |
|---|---|---|
| Anterior | Growth hormone (GH) | Promotes growth of body tissues |
| Anterior | Prolactin (PRL) | Promotes milk production from mammary glands |
| Anterior | Thyroid-stimulating hormone (TSH) | Stimulates thyroid hormone release from thyroid |
| Anterior | Adrenocorticotropic hormone (ACTH) | Stimulates hormone release by adrenal cortex |
| Anterior | Follicle-stimulating hormone (FSH) | Stimulates gamete production in gonads |
| Anterior | Luteinizing hormone (LH) | Stimulates androgen production by gonads |
| Posterior | Antidiuretic hormone (ADH) / Vasopressin | Stimulates water reabsorption by kidneys |
| Posterior | Oxytocin | Stimulates smooth muscle contractions in male and female reproductive tracts and uterine contractions during childbirth |
Concept Review
The hypothalamus–pituitary complex is located in the diencephalon of the brain. The hypothalamus and the pituitary gland are connected by a structure called the infundibulum, which contains vasculature and nerve axons. The pituitary gland is divided into two distinct structures with different embryonic origins. The posterior lobe houses the axon terminals of hypothalamic neurons. It stores and releases into the bloodstream two hypothalamic hormones: oxytocin (OT) and antidiuretic hormone (ADH). The anterior lobe is connected to the hypothalamus by the vasculature of the hypophyseal portal system in the infundibulum and produces and secretes six hormones. Their secretion is regulated, however, by releasing and inhibiting hormones from the hypothalamus. The six anterior pituitary hormones are: growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL). Figure \(\PageIndex{4}\) is a summary of the pituitary hormones and their principal effects.
