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 and antidiuretic hormone (ADH). The anterior lobe is connected to the hypothalamus by vasculature 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).
acromegaly
disorder in adults caused when abnormally high levels of GH trigger growth of bones in the face, hands, and feet
adrenocorticotropic hormone (ACTH)
anterior pituitary hormone that stimulates the adrenal cortex to secrete corticosteroid hormones (also called corticotropin)
antidiuretic hormone (ADH)
hypothalamic hormone that is stored by the posterior pituitary and that signals the kidneys to reabsorb water
follicle-stimulating hormone (FSH)
anterior pituitary hormone that stimulates the production and maturation of sex cells
gigantism
disorder in children caused when abnormally high levels of GH prompt excessive growth
gonadotropins
hormones that regulate the function of the gonads
growth hormone (GH)
anterior pituitary hormone that promotes tissue building and influences nutrient metabolism (also called somatotropin)
hypophyseal portal system
network of blood vessels that enables hypothalamic hormones to travel into the anterior lobe of the pituitary without entering the systemic circulation
hypothalamus
region of the diencephalon inferior to the thalamus that functions in neural and endocrine signaling
infundibulum
stalk containing vasculature and neural tissue that connects the pituitary gland to the hypothalamus (also called the pituitary stalk)
insulin-like growth factors (IGF)
protein that enhances cellular proliferation, inhibits apoptosis, and stimulates the cellular uptake of amino acids for protein synthesis
luteinizing hormone (LH)
anterior pituitary hormone that triggers ovulation and the production of ovarian hormones in females, and the production of testosterone in males
osmoreceptor
hypothalamic sensory receptor that is stimulated by changes in solute concentration (osmotic pressure) in the blood
oxytocin
hypothalamic hormone stored in the posterior pituitary gland and important in stimulating uterine contractions in labor, milk ejection during breastfeeding, and feelings of attachment (also produced in males)
pituitary dwarfism
disorder in children caused when abnormally low levels of GH result in growth retardation
pituitary gland
bean-sized organ suspended from the hypothalamus that produces, stores, and secretes hormones in response to hypothalamic stimulation (also called hypophysis)
prolactin (PRL)
anterior pituitary hormone that promotes development of the mammary glands and the production of breast milk
thyroid-stimulating hormone (TSH)
anterior pituitary hormone that triggers secretion of thyroid hormones by the thyroid gland (also called thyrotropin)
Visit this link to watch an animation showing the role of the hypothalamus and the pituitary gland. Which hormone is released by the pituitary to stimulate the thyroid gland?
Thyroid-stimulating hormone.
1. The hypothalamus is functionally and anatomically connected to the posterior pituitary lobe by a bridge of ________.
A) blood vessels
B) nerve axons
C) cartilage
D) bone
B
2. Which of the following is an anterior pituitary hormone?
A) ADH
B) oxytocin
C) TSH
D) cortisol
C
3. How many hormones are produced by the posterior pituitary?
A) 0
B) 1
C) 2
D) 6
A
4. Which of the following hormones contributes to the regulation of the body’s fluid and electrolyte balance?
A) adrenocorticotropic hormone
B) antidiuretic hormone
C) luteinizing hormone
D) all of the above
B
1. Compare and contrast the anatomical relationship of the anterior and posterior lobes of the pituitary gland to the hypothalamus.
The anterior lobe of the pituitary gland is connected to the hypothalamus by vasculature, which allows regulating hormones from the hypothalamus to travel to the anterior pituitary. In contrast, the posterior lobe is connected to the hypothalamus by a bridge of nerve axons called the hypothalamic–hypophyseal tract, along which the hypothalamus sends hormones produced by hypothalamic nerve cell bodies to the posterior pituitary for storage and release into the circulation.
2. Name the target tissues for prolactin.
The mammary glands are the target tissues for prolactin.