Thyroid Gland Anatomy and Physiology

Study Notes

The thyroid gland is a butterfly-shaped organ located anterior to the trachea and inferior to the larynx.
It is comprised of two lobes, left and right, connected by an area called the isthmus.
Parathyroid glands are located on the posterior surface of the thyroid lobes.
The thyroid gland secretes two main hormones: triiodothyronine (T3) and thyroxine (T4).
Iodine is a crucial component of thyroid hormones, obtained through diet.

The Hypothalamic-Pituitary-Thyroid Axis involves a complex interplay of hormones.
The hypothalamus releases thyrotropin-releasing hormone (TRH), which stimulates the pituitary gland to produce thyroid-stimulating hormone (TSH).
TSH then acts on the thyroid gland to release T3 and T4.

T3 and T4 regulate numerous vital body functions, including:
- Growth and development
- Basal metabolic rate
- Heat production
- Metabolism of carbohydrates, proteins, and fats
- Central nervous system function
- Body temperature, heart rate, and blood pressure
- Weight
- Sexual ability
Calcitonin, another hormone secreted by the thyroid gland, plays a role in calcium regulation:
- Decreases blood calcium levels when elevated
- Promotes calcium storage in bones
- Inhibits calcium reabsorption from renal tubules.

Calcitonin and PTH work together to maintain blood calcium levels within a narrow range.
Calcitonin lowers blood calcium levels, while PTH raises them.

Hyperthyroidism (overactive thyroid): Occurs when the thyroid gland produces excessive thyroid hormones.
Hypothyroidism (underactive thyroid): Occurs when the thyroid gland does not produce enough thyroid hormones to meet the body's needs.

Hyperthyroidism
- Increased metabolism
- Weight loss
- Rapid heartbeat (tachycardia)
- Tremors
- Difficulty sleeping
- Increased appetite
- Heat intolerance
- Nervousness
- Irritability
- Goiter (enlarged thyroid gland)
- Eye problems (bulging eyes)
- Diarrhea
- Hair loss
- Menstrual irregularities
Hypothyroidism
- Fatigue
- Weight gain
- Slow heartbeat (bradycardia)
- Constipation
- Dry skin
- Cold intolerance
- Depression
- Memory problems
- Hoarse voice
- Goiter (enlarged thyroid gland)
- Irregular menstrual periods
- Infertility
- Muscle weakness
- Joint stiffness

Hyperthyroidism
- Thyroid storm: a rare but life-threatening complication characterized by extreme hyperthyroidism symptoms.
Hypothyroidism
- Myxedema: a severe form of hypothyroidism that requires immediate medical attention.

Medical
- Antithyroid medications
- Synthetic thyroid hormone replacement therapy
- Beta blockers to manage symptoms
Surgical
- Removal of part or all of the thyroid gland (thyroidectomy)
Nursing
- Monitoring vital signs
- Education about medication and lifestyle changes
- Assessing for complications
- Providing emotional support
- Teaching self-management skills