Human Endocrine System

Glucocorticoids (such as cortisol) are catabolic hormones that stimulate proteolysis - the breakdown of proteins into amino acids, particularly during fasting, stress, or hibernation. These amino acids can then be used for gluconeogenesis to maintain blood glucose levels. Secretin stimulates digestive secretions, adrenalin (epinephrine) is primarily involved in acute stress response, and enterogastrone inhibits gastric secretions.

Prolactin is a peptide hormone produced by the anterior pituitary gland that stimulates milk production. Testosterone, oestradiol-17B, and progesterone are all steroid hormones derived from cholesterol, characterized by their four-ring structure. Steroid hormones include sex hormones (androgens, estrogens, progestins) and corticosteroids.

Oestrogens, androgens, progestins, and corticosteroids are all classes of steroid hormones. They share a common chemical structure based on four fused rings and are synthesized from cholesterol. Prostaglandins are lipid-derived eicosanoids, juvenile hormones are insect growth regulators, and these options don't fit the classification.

Glucagon is the primary hormone that increases blood glucose levels during fasting, exercise, or stress. It stimulates glycogenolysis (breakdown of glycogen to glucose) in the liver and gluconeogenesis (formation of glucose from non-carbohydrate sources). Insulin lowers blood glucose by promoting glucose uptake, somatostatin inhibits both glucagon and insulin secretion, so 'all of the above' is incorrect.

Melatonin inhibits estrous (reproductive cycle) in healthy rats, particularly in response to longer dark periods (winter conditions). Melatonin is secreted by the pineal gland in response to darkness and regulates seasonal reproductive cycles in many mammals. It can suppress estrous in light-induced constant estrous rats by maintaining natural photoperiodic signaling.

Androgens (such as testosterone) are primarily secreted by the testes in males. While the adrenal cortex does produce small amounts of androgens, the testes are the main source. The ovaries produce small amounts of androgens as precursors to estrogen, and the parathyroid secretes parathyroid hormone, not androgens. Therefore, the testis is the correct answer as the primary androgen-secreting gland.

Clomiphene and Tamoxifen are selective estrogen receptor modulators (SERMs) that act as antiestrogens. They block estrogen receptors in certain tissues - Clomiphene is used for ovulation induction, while Tamoxifen treats estrogen receptor-positive breast cancer.

Follicle-stimulating hormone (FSH) causes maturation of a cohort of early-stage ovarian follicles; one of these will ultimately become the dominant, or Graafian follicle.

Yes, it is correct. The endocrine system works closely with the nervous system in regulating certain activities of the body by secreting hormones directly into the bloodstream.

Yes, it is correct. Testosterone is the male sex hormone. 

The endocrine glands secrete them in small amounts.

Thyroxine hormone regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth. It has influence over physical and mental development of an individual.

Human insulin is a polypeptide of 51 amino acids arranged in two chains (A and B) bearing 21 and 30 amino acids, respectively.

Progestin (progesterone) and estrogen both are used for making oral contraceptives.