Micronutrient Metabolism: Minerals

Flashcards reviewing key concepts about minerals, calcium, iodine, thyroid hormones, iron, zinc, copper, chromium, selenium, and fluorine metabolism.

What percentage of the body's elements are mineral elements?

4%

What is the daily requirement level for macro minerals?

100 mg/day

Give an example of a nutritionally essential mineral.

Fe, I, Cu, Mn, Zn, Se

What is the most abundant mineral in the body?

Calcium

What percentage of calcium is stored in bones?

99%

Name three functions of calcium in the body.

Bone and teeth development, muscle contraction, nerve excitation, blood clotting, cell junction stabilization, intracellular messenger, hormone mediation

In what form is calcium stored in bone?

Hydroxyapatite

What are the three forms of calcium in serum?

Ionized and diffusible, unionized and diffusible, bound to protein

What is the percentage of ionized and diffusible calcium present in blood plasma?

50%

What is the normal range of total plasma calcium concentration?

2.2 – 2.6 mmol/L

Which fraction of calcium in the blood plasma is physiologically active?

Free ionized calcium

What is the recommended daily calcium intake for adults?

400-500 mg/d

What is the recommended calcium intake for pregnant and lactating women?

1000-1200 mg/d

Where is the primary site of calcium absorption in the intestine?

Duodenum and jejunum

What percentage of dietary calcium is absorbed?

20-30%

Which vitamin regulates active calcium absorption?

Vitamin D (1, 25 dihydroxycholecalciferol)

Name three factors that increase calcium absorption.

Vitamin D, Gastric HCl, Basic amino acids, lysine and arginine, Hypocalcemia, High protein diet

Name three factors that decrease calcium absorption.

Oxalic acid, Phytic acid, Increased fat content in diet, Steatorrhea

Name three hormones that regulate serum calcium levels.

Parathyroid hormone (PTH), 1, 25 Dihydroxycholecalciferol (calcitriol), Calcitonin

What is the effect of parathyroid hormone (PTH) on serum calcium levels?

Increases serum calcium by increasing osteoclastic activity, decreasing renal phosphate reabsorption, and increasing calcitriol formation.

What is the effect of calcitriol on serum calcium levels?

Increases serum calcium by increasing intestinal absorption and renal reabsorption, and stimulating osteoclastic activity.

What is the effect of calcitonin on serum calcium levels?

Decreases serum calcium by decreasing osteoclastic activity and increasing urinary excretion of calcium.

How is most of the ingested calcium excreted?

In the feces 70 to 80

What is the daily iodine requirement for healthy adults?

100-150 µg /day

What is the daily iodine requirement for infants?

20-40 µg /day

What are two thyroid hormones made using iodine?

Triiodothyronine (T3 ) and thyroxine (T4 )

What are some dietary sources of iodine?

Salts, Sea food, Vegetables, Fruits grown in coastal areas, Drinking water, Coconut, Iodized salts

Where does the synthesis of thyroid hormones occur?

Follicular cells of the thyroid gland

What is the glycoprotein stored in the thyroid follicle colloid?

Thyroglobulin

What are the three stages of T3 and T4 production?

Iodide entry, oxidation and binding to tyrosine residues, proteolysis and secretion

Which enzyme catalyzes the oxidation of iodide to todine?

Thyroperoxidase (TPO)

Which hormone is responsible for regulating the synthesis and secretion of thyroid hormone?

Thyrotropin (TSH - Thyroid Stimulating Hormone)

What percentage of T4 is bound to protein?

99.98%

List three transport proteins for T4.

Thyroxine binding globulin (TBG), Transthyretin, Albumin

Which thyroid hormone is more biologically active?

T3

What is hyperthyroidism?

Excessive secretion of thyroid hormone

What is hypothyroidism?

Deficiency of thyroid hormone secretion

Name two major causes for hyperthyroidism

Grave’s disease, Toxic nodular goiter

What are two main types of hypothyroidism?

Primary and secondary

Name three classifications of primary hypothyroidism.

Spontaneous atrophic hypothyroidism, Goitrous hypothyroidism, Sub clinical hypothyroidism

Other than medication that is used to treat hyperthyroidism, what are two other treatments?

Surgery (sub total thyroidectomy), radio active iodine (131 I).

What is the best test for plasma T4 if there are abnormalities of binding protiens?

Plasma Free Thyroxine (Free T4)

Which plasma test can be used for hyperthyroidism, but not hypothyroidism?

Plasma total or Free (T3)

What are the four functional groups of iron

Haemoglobin iron (70%), Tissue iron (25%), Storage iron (3%), Transport iron (2%)

Where does maximal iron absorption occur?

Duodenum

Name two causes of iron overload.

Increased intake and absorption of iron, Prolonged parenteral administration of iron or repeated blood transfusions

Name two functions related to copper.

Aids in binding Fe+3 to apotransferrin, Fe3+ - transferrin, Important in cholesterol and glucose metabolism, immune functions and protection, Against oxidative stress, Important in oxidative phosphorylation in liver, muscle and nerve tissue, Component of monoamine oxidase system in elastic and connective tissues