Pituitary and hypothalamic hormones are derived from proteins or amino acids (non-steroid) and are water-soluble. These hormones are stored in vesicles and the endoplasmic reticulum of endocrine cells until needed.
Some examples of hormones produced by the hypothalamus include:
- Corticotropin-releasing hormone (CRH)
- Growth hormone-releasing hormone (GHRH)
- Somatostatin, also referred to as growth hormone inhibiting hormone (GHIH)
- Gonadotropin-releasing hormone (GRH)
- Thyrotropin-releasing hormone (TRH)
- Oxytocin
- Antidiuretic hormone (ADH), also referred to as vasopressin
Some examples of hormones produced by the pituitary gland include:
- Adrenocorticotropic hormone (ACTH)
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Growth hormone (GH)
- Prolactin (PRL)
- Thyroid-simulating hormone (TSH)
Amino acid hormones are relatively small molecules and function by binding to protein receptors on the outside surface of the cell. This binding creates a second messenger molecule cascade inside the cell that activates enzymes and other cellular proteins or influences gene expression. Examples of amino acid hormones include the adrenal hormones epinephrine and norepinephrine.
Polypeptide hormones like insulin, growth hormone, and prolactin consist of long chains of amino acids held together by peptide bonds. These protein hormones are stored in endocrine cells until needed to regulate functions such as metabolism, lactation, growth, and reproduction.
In the image to the right, the purple dots are polypeptide hormones (a) that bind directly to transmembranous proteins located on the plasma membrane (b). Upon entry into the cell, there is intracellular messaging from the cytoplasm (c), which ultimately ends in the nucleus (d).
More details regarding the hypothalamus and pituitary gland and the hormones produced by each will be introduced later in the course.
