Thyroid Gland and Calcium Homeostasis

Thyroid gland

produces thyroid hormone

Thyroid follicle/follicle cells

produce the thyroid hormone

Parafollicular cells (C cells)

cells found between follicles in the thyroid

Colloid

glycoprotein that fills the interior space of the follicles, it is produced by the follicle cells; it is the storage form of thyroid hormone

Thyrotropin Releasing Hormone (TRH)

hormone produced by the hypothalamus that regulates the action of the anterior pituitary to release TSH

Thyrotrophs

cells in the anterior pituitary that produce TSH

Thyroid Stimulating Hormone (TSH)

hormone produced in the anterior pituitary gland that stimulates the action of follicle cells in the thyroid

Thyroid Hormone

regulation of metabolic rate and thermoregulation, promotion of growth and development, synergism with the sympathetic nervous system

T3

10% of thyroid hormone produced, but is 20x more biologically active than T4

T4\=Thyroxine

90% of thyroid hormone that is produced

Iodide

enters the follicle cells from your diet and embeds itself in the colloid to become part of the thyroid hormone

Thyroglobulin

large molecules found in the colloid that is broken down into T3 and T4 when thyroid hormone is needed

Thyroid binding globulin

a protein that transports thyroid hormone in the plasma

Basal metabolic rate

the amount of energy required at rest; thyroid hormone increases this rate

Thermoregulation

cell activity releases heat and helps maintain body temperature; your BMR has a direct impact on core body temp

Hypothyroidism

not enough thyroid hormone being produced

Goiter

enlarged thyroid due to excessive stimulation by TSH when the thyroid cannot produce thyroid hormone

Hashimoto’s Disease

autoimmune antibodies destroy thyroid gland (due to high levels of circulating TSH) causing hypothyroidism

Hyperthyroidism

overactive thyroid gland producing too much thyroid hormone

Grave’s Disease

autoimmune antibodies activate TSH receptors resulting in increased T3/T4 production with low circulating TSH

Parathyroid hormone

created in the parathyroid gland that increases calcium concentrations in the plasma by affecting function in bone, kidney, and intestines

Calcitriol (Vitamin D3)

facilitates in the intestinal absorption of calcium; helps with renal absorption and mobilization from bone

Calcitonin

produced by the parafollicular cells in the thyroid, functions to reduce plasma calcium concentrations (opposite of PTH and Calcitriol), has a lesser effect than the other 2 hormones