A hormone produces its effect by binding to a target cell's receptors for that hormone. The more receptors it binds to, the greater is the effect on the target cell. All hormones affect target cells by altering their metabolic activities. For example, they may change the rate of cellular processes in general, or they may [...]
The pituitary gland, or hypophysis, is attached to the hypothalamus by a short stalk. It rests in a depression of the sphenoid bone, the sella turcica, which provides protection. The pituitary gland consists of two major parts that have different functions: an anterior lobe and a posterior lobe. Although the pituitary gland is small, it [...]
The thyroid gland is located just inferior to the larynx. It consists of two lobes, each one lateral to the trachea, that are connected by an anterior isthmus. Hormones of the Thyroid Gland Hormone Control Action Disorders Thyroxine (T4) and triiodothyronine (T3) TSH from anterior lobe of the pituitary gland Increase metabolic rate; accelerate growth; [...]
There are two adrenal glands; one is located on top of each kidney. Each adrenal gland consists of two portions that are distinct endocrine glands: the deep adrenal medulla and the superficial adrenal cortex. Hormones of The Adrenal Glands Hormone Control Action Disorders Adrenal Medulla Epinephrine Sympathetic division of Prepare body to meet emergencies; Hypersecretion [...]
Plasma calcium levels are regulated by the polypeptides parathyroid hormone and calcitonin. Parathyroid hormone, secreted by the parathyroid glands embedded in the thyroid, acts to increase plasma calcium levels. Parathyroid hormone also decreases plasma PO4. Calcitonin, secreted from the parafollicular cells of the thyroid, acts to decrease plasma Ca++. of the two hormones, parathyroid hormone [...]
Both males and females possess mammary glands. The mammary glands of males and immature females are similar. At puberty, estrogens and progesterone stimulate the development of female mammary glands. Estrogens start breast and mammary gland development, and progesterone stimulates the maturation of the mammary glands so that they are capable of secreting milk. Another hormone [...]
High blood levels of estrogens and progesterone during pregnancy stimulate the development of the mammary glands and enlargement of the breasts in preparation for milk secretion, or lactation (lak-ta'-shun). Although the mammary glands are capable of secreting milk, the high levels of estrogens and progesterone inhibit the hypothalamus so that milk secretion does not occur [...]