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The gonads—the male testes and female ovaries—produce steroid hormones. The testes produce androgens, testosterone being the most prominent, which allow for the development of secondary sex characteristics and the production of sperm cells. The ovaries produce estradiol and progesterone, which cause secondary sex characteristics and prepare the body for childbirth.
| Endocrine Glands and their Associated Hormones | ||
|---|---|---|
| Endocrine Gland | Associated Hormones | Effect |
| Hypothalamus | releasing and inhibiting hormones | regulate hormone release from pituitary gland; produce oxytocin; produce uterine contractions and milk secretion in females |
| antidiuretic hormone (ADH) | water reabsorption from kidneys; vasoconstriction to increase blood pressure | |
| Pituitary (Anterior) | growth hormone (GH) | promotes growth of body tissues, protein synthesis; metabolic functions |
| prolactin (PRL) | promotes milk production | |
| thyroid stimulating hormone (TSH) | stimulates thyroid hormone release | |
| adrenocorticotropic hormone (ACTH) | stimulates hormone release by adrenal cortex, glucocorticoids | |
| follicle-stimulating hormone (FSH) | stimulates gamete production (both ova and sperm); secretion of estradiol | |
| luteinizing hormone (LH) | stimulates androgen production by gonads; ovulation, secretion of progesterone | |
| melanocyte-stimulating hormone (MSH) | stimulates melanocytes of the skin increasing melanin pigment production. | |
| Pituitary (Posterior) | antidiuretic hormone (ADH) | stimulates water reabsorption by kidneys |
| oxytocin | stimulates uterine contractions during childbirth; milk ejection; stimulates ductus deferens and prostate gland contraction during emission | |
| Thyroid | thyroxine, triiodothyronine | stimulate and maintain metabolism; growth and development |
| calcitonin | reduces blood Ca 2+ levels | |
| Parathyroid | parathyroid hormone (PTH) | increases blood Ca 2+ levels |
| Adrenal (Cortex) | aldosterone | increases blood Na + levels; increase K + secretion |
| cortisol, corticosterone, cortisone | increase blood glucose levels; anti-inflammatory effects | |
| Adrenal (Medulla) | epinephrine, norepinephrine | stimulate fight-or-flight response; increase blood gluclose levels; increase metabolic activities |
| Pancreas | insulin | reduces blood glucose levels |
| glucagon | increases blood glucose levels | |
| Pineal gland | melatonin | regulates some biological rhythms and protects CNS from free radicals |
| Testes | androgens | regulate, promote, increase or maintain sperm production; male secondary sexual characteristics |
| Ovaries | estrogen | promotes uterine lining growth; female secondary sexual characteristics |
| progestins | promote and maintain uterine lining growth |
The pituitary gland is located at the base of the brain and is attached to the hypothalamus by the infundibulum. The anterior pituitary receives products from the hypothalamus by the hypophyseal portal system and produces six hormones. The posterior pituitary is an extension of the brain and releases hormones (antidiuretic hormone and oxytocin) produced by the hypothalamus.
The thyroid gland is located in the neck and is composed of two lobes connected by the isthmus. The thyroid is made up of follicle cells that produce the hormones thyroxine and triiodothyronine. Parafollicular cells of the thyroid produce calcitonin. The parathyroid glands lie on the posterior surface of the thyroid gland and produce parathyroid hormone.
The adrenal glands are located on top of the kidneys and consist of the renal cortex and renal medulla. The adrenal cortex is the outer part of the adrenal gland and produces the corticosteroids, glucocorticoids, and mineralocorticoids. The adrenal medulla is the inner part of the adrenal gland and produces the catecholamines epinephrine and norepinephrine.
The pancreas lies in the abdomen between the stomach and the small intestine. Clusters of endocrine cells in the pancreas form the islets of Langerhans, which are composed of alpha cells that release glucagon and beta cells that release insulin.
Some organs possess endocrine activity as a secondary function but have another primary function. The heart produces the hormone atrial natriuretic peptide, which functions to reduce blood volume, pressure, and Na + concentration. The gastrointestinal tract produces various hormones that aid in digestion. The kidneys produce renin, calcitriol, and erythropoietin. Adipose tissue produces leptin, which promotes satiety signals in the brain.
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