Thyroid Physiology Quiz

An endocrine gland located at the base of the neck, responsible for producing and releasing thyroid hormones.

Specialized cells lining the follicles of the thyroid gland. They produce thyroid hormone.

The gelatinous substance found inside the thyroid follicles. It's a major component of thyroid hormone.

A large glycoprotein found in colloid. It's a precursor to thyroid hormones.

The primary thyroid hormone (T4), responsible for controlling metabolism.

Another thyroid hormone (T3), also involved in metabolism. It's more potent than T4.

A hormone secreted by the pituitary gland. It controls the production and release of thyroid hormones.

Thyroid function is affected by different stages of the sexual cycle. It increases during pregnancy and lactation, and decreases during menopause.

The active transport of iodide from the blood into follicular cells, going against the electrochemical gradient.

A protein pump in follicular cells responsible for transporting iodide along with sodium, concentrating iodide in the thyroid gland.

The oxidation of iodide into elementary iodine, facilitated by thyroid peroxidase within the follicular cells.

The transport of iodine from the follicular cells into the follicular cavity, mediated by the iodide-chloride pump known as pendrin.

The process of iodine combining with tyrosine, forming iodotyrosine residues.

The coupling of iodotyrosine residues to create different thyroid hormones.

The process of coupling monoiodotyrosine (MIT) and di-iodotyrosine (DIT) to form triiodothyronine (T3).

The coupling of di-iodotyrosine (DIT) and di-iodotyrosine (DIT) to form tetraiodothyronine or thyroxine (T4).

Thyroxine increases the force of the heart contraction, but excess thyroxine can weaken the heart due to increased metabolic activity and protein breakdown.

Thyroxine causes vasodilation by increasing metabolic activities.

Increased metabolism caused by thyroxine boosts oxygen demand and carbon dioxide production, stimulating respiratory centers to increase rate and force of respiration.

Thyroxine stimulates appetite and food intake, increases gastrointestinal secretions and movements.

Thyroxine is crucial for developing and maintaining normal central nervous system function.

Thyroxine contributes to the formation of synapses between neurons and the myelin sheath that insulates axons.

Thyroxine is needed for the normal functioning of skeletal muscles.

Thyroid hormone, within physiological limits, enhances protein synthesis by boosting RNA translation, DNA transcription to RNA, mitochondrial activity, and cellular enzyme activity.

Increased thyroid hormone levels shift the balance towards protein breakdown, particularly in muscles, leading to muscle weakness, a condition known as thyrotoxic myopathy.

Insufficient thyroid hormone results in sluggish muscles, slow relaxation after contraction, and potential muscle weakness.

Thyroid hormone promotes glucose absorption from the intestines and boosts glucose uptake by cells. It also accelerates glycogen breakdown and gluconeogenesis, increasing blood glucose levels.

Thyroid hormone mobilizes fats from adipose tissue, raising blood levels of free fatty acids. This process contributes to fat breakdown.

Despite increased blood levels of free fatty acids, thyroid hormone reduces cholesterol, phospholipids, and triglyceride levels in plasma. However, hyposecretion leads to high cholesterol and potential atherosclerosis. It also increases liver fat deposition.

Low levels of thyroid hormone lead to high cholesterol in plasma, making atherosclerosis more likely. This occurs due to low T4 production.

Thyroid hormone increases the excretion of cholesterol from liver cells into bile, lowering blood cholesterol levels. It achieves this by inducing more LDL receptors on liver cells, leading to a faster uptake of LDLs from the plasma.

TSH, or Thyroid-stimulating hormone, is a crucial peptide hormone secreted by the pituitary gland. It plays a vital role in regulating thyroid function by stimulating the production and release of thyroid hormones (T3 and T4).

TSH has a lifespan of about 60 minutes in the bloodstream. This means it breaks down and is removed from the body relatively quickly.

The typical level of TSH in a healthy person's blood is about 2 U/mL, which stands for units per milliliter. This indicates the amount of TSH present in a tiny sample of blood.

TSH's primary action is to stimulate the thyroid gland, a butterfly-shaped organ in the neck, to increase its activity. This includes boosting the production of thyroid hormones and influencing the growth and function of thyroid cells.

The hypothalamus, a tiny region in the brain, plays a key role in regulating TSH release. It secretes a hormone called TRH (Thyrotropin-releasing hormone), which acts on the pituitary gland to stimulate the production and release of TSH.

Thyroid hormones exhibit a negative feedback mechanism, meaning they regulate their own production. When thyroid hormone levels rise, they signal the hypothalamus and pituitary to reduce TSH production, in turn decreasing thyroid hormone production.

Thyroid hormones have a wide range of functions, including increasing the body's metabolic rate, influencing growth and development, and regulating many bodily functions. They are crucial for overall health and well-being.

Thyroid hormones, particularly T4, can increase the body's metabolic rate, which refers to the rate at which energy is produced. This is often called the calorigenic action of thyroid hormones.

A condition caused by excessive thyroxine, leading to muscle weakness due to protein breakdown.

Fine, rapid muscle tremor occurring at a frequency of 10-15 times per second due to increased neuronal activity caused by excess thyroxine.

The inability to sleep well due to hyperthyroidism, despite feeling tired and exhausted.

Excessive sleepiness characterized by long sleep durations, often 12-14 hours a day, due to hypothyroidism.

Loss of libido in men due to hypothyroidism.

Heavy and prolonged menstrual bleeding in women due to hypothyroidism.

Frequent menstrual cycles in women due to hypothyroidism.

Thyroid hormones increase the demand for hormones from other endocrine glands.