General Biology - NCLEX-PN

The nutrients specifically required for thyroid hormone production are tyrosine, iodine, and selenium, in addition to zinc and several B vitamins. While magnesium, manganese, and methionine are all essential for metabolism and overall hormone production, they are not direct substrates or cofactors in the production of thyroid hormone.

Tyrosine and iodine are both precursors for synthesis of T4. Selenium is essential for conversion of T4 to T3, and iron is the cofactor for conversion of phenylalanine into tyrosine.

Selenium is essential for conversion of T4 to T3. Deiodinase enzymes, which remove iodine from T4 during conversion into T3, are selenium dependent. Tyrosine and iodine are both required for synthesis of T4, and iron is the cofactor for conversion of phenylalanine into tyrosine.

Calcitonin is produced by the parafollicular (c cells) of the thyroid as a response to elevated blood calcium levels. Calcitonin reduces plasma calcium by inhibiting osteoclast activity and stimulating osteoblasts to deposit more bone. Parathyroid hormone has the opposite effect - it acts to increase calcium levels when serum calcium decreases. While they may ultimately affect serum calcium levels, thyroid hormone and cortisol are not directly involved in calcium homeostasis.

Thyroid-stimulating hormone (TSH) is produced in the anterior pituitary. Somatostatin, dopamine, and gonadotropin releasing hormone are all hypothalamic hormones. Somatostatin is also secreted by the pancreas, and slows down digestive processes. To remember the hormones of the anterior pituitary, use the following mnemonic: FLAT PEG, Follicle-stimulating hormone, Luteinizing hormone, Adrenocorticotropic hormone, Thyroid-stimulating hormone, Prolactin, Endorphins, Growth hormone.

Calcitonin is produced by the thyroid gland. The hormone plays an important role in lowering blood calcium levels. It is also synthesized as a drug and used in the treatment of hypercalcemia. The other three hormones are indeed secreted by the islets of Langerhans in the pancreas. Insulin, secreted by the beta cells lowers blood sugar, glucagon, secreted by the alpha cells, increases blood sugar, and somatostatin, secreted by the gamma cells regulates digestive and metabolic processes. Lipase is not a hormone, but an enzyme that facilitates the breakdown of lipids. The pancreas does indeed secrete lipase.

Endocrine glands secrete hormones into the blood. The endocrine glands include the ovaries, testes, hypothalamus, thyroid, pituitary, adrenal glands, pancreas, the pineal gland, and others. Salivary glands are considered exocrine glands. Exocrine glands secrete substances through ducts to the body surface or into body cavities, such as the mouth in the case of salivary glands.

Oxytocin is produced by the hypothalamus, and is released by the posterior pituitary. Women experience an increased level of oxytocin during labor, after birth, and while breastfeeding. It helps to increase uterine contractility, aiding in the delivery process and preventing hemorrhage after birth. Progesterone and estrogen are hormones released from the ovary. Estrogen is has many effects on the body, one of which is the development of sex characteristics in females. Progesterone is important in regulation of the uterine lining. Prolactin is made by the anterior pituitary gland and functions in the production on breast milk.

Epinephrine is the only hormone of those listed that is produced by the adrenal medulla. The adrenal medulla is the center of the adrenal gland. Antidiuretic hormone is produced by the posterior pituitary. Calcitonin is produced by the thyroid. Thyroid-stimulating hormone is secreted from the anterior pituitary, as is follicle-stimulating hormone.

All of these are correct effects of parathyroid hormone. The kidneys resorb calcium and as a result, less is released into the urine. The intestines absorb additional calcium from food and calcium is released from the bone through the work of osteoclasts.

Catecholamines are hormones produced by the adrenal medulla. Adrenal glands are located above each kidney. Catecholamines may also function as neurotransmitters, important chemical messengers. They regulate the sympathetic nervous system's response to stress.

Thyroid-stimulating hormone (TSH) is produced by the anterior pituitary. TSH causes the thyroid to release thyroid hormones (T3 and T4). A TSH blood test is often ordered to diagnose hypoactive thyroid.

The thyroid gland is located (in front) anterior to the trachea. The parathyroid glands are located on the backside on the thyroid. The thyroid is stimulated in response to TSH produced by the anterior pituitary. It will then secrete T3 and T4 although T3 is more potent and produced in a lesser quantity. Calcitonin, a hormone which decreases blood calcium levels, is also produced by the thyroid.

Aldosterone is a hormone secreted by the adrenal glands. Serum aldosterone levels vary throughout the day. Aldosterone presence is highest in the morning. Of the answer choices, 7 AM is the best choice. A physician may have the patient come to the office at a specific time of day for this reason.

The pineal gland is responsible for regulating melatonin. It is not known at this time to secrete any other hormone. Melatonin is thought to play a critical role in the regulation of the circadian rhythm. Cortisol is secreted by the adrenal cortex and is involved in regulating the stress response. Vitamin D become activated in three steps. First, ultraviolet light in the skin begins the process, then the process continues in the liver, and is completed in the kidney. The active form of vitamin D increases calcium absorption in the gut, decreases calcium loss in urine, and increases calcium mobilization from bone. Vasopressin is also known as antidiuretic hormone, and functions in water retention. Leptin is a hormone secreted by adipose tissue that tells the body that it is full, and not hungry.

Leptin is secreted by adipose cells, and acts on the arcuate nucleus of the lateral hypothalamus to promote the synthesis of alpha-MSH (alpha-melanocyte-stimulating hormone), which is a hunger suppressant. It also binds to receptors for neuropeptide Y (NPY), a powerful hunger promoter, in the arcuate nucleus.

None of the other hormones listed, while all involved in nutrient and blood sugar metabolism, directly trigger feeling of satiety.

Leptin, the hormone responsible for feelings of satiety, goes down during times of fasting, with high testosterone, during sleep deprivation, and during periods of prolonged exercise or physical training.

Insulin has many physiological effects on metabolism. It increases uptake of glucose and various ions, especially potassium, from the blood. It promotes glycogen and protein synthesis, and encourages storage of fats. Conversely, insulin inhibits lipolysis, gluconeogenesis, ketogenesis, and proteolysis.

IgA, primarily in its secretory form (sIgA), is the most abundant immunoglobulin in the lining of the gastrointestinal tract and in the mucus membranes of the respiratory tract. It is also present in the urogenital tract, in tears, in saliva, and in breast milk. All of the other immunoglobulins may be present in mucus membranes, depending on the presence of active infection or allergy, but none is as abundant in secretions as IgA. IgE is primarily involved in binding allergens and inducing the allergic response via release of histamine. IgM is expressed on the surface of B cells and is the first immunoglobulin to fight pathogens at the site of infection/injury. IgG are the most abundant antibody throughout the body and play the largest role in fighting pathogens. IgG can cross the placenta and thus confer passive immunity to the fetus.

The presence of CMV IgM would suggest an active cytomegalovirus infection, as IgM is the immunoglobulin released during the initial, active infection with a pathogen. The presence of IgG would suggest a past infection, where IgG specific to the virus would be present as part of adaptive immunity (ready to respond to the virus should the host ever be re-exposed). IgE is not formed when an individual contracts CMV, as IgE is produced in response to allergens rather than pathogens (except parasites). The function of IgD is thought to be related to the allergic response by regulating basophils and mast cells.