THYROID GLANDChloe Benner and Michelle Olson

LOCATION

• Situated in the anterior part of the neck

• “Adams’ apple”

• Originates in the back of the tongue

• Shape of a butterfly

• Normally not outwardly visible

• Biggest gland in the neck

CLASS OF HORMONE

• Produces hormones which regulate: • Metabolic rate • Heart and digestive function• Muscle control • Brain development • Bone maintenance

• Thyroxine (T4)

• Triiodothyionine (T3)• Calcitonin

Thyroxine (T4)

Triiodothyionine (T3)

CELL SIGNALING PATHWAY• Steroid hormone

• Thyroid hormone synthesized from tyrosine

• Water or lipid soluble• Steroid and thyroid hormones are

hydrophobic • Can easily pass through the plasma

membrane• Bind to specific receptor proteins

• TSH then acts on the cells in the thyroid gland • Initiate the synthesis and secretion of the

thyroid hormone

• Stimulates a variety of metabolic processes that maintain body temperature

FEEDBACK(POSITIVE AND NEGATIVE)

• Positive feedback is much less common than negative feedback.

• Negative Feedback• Hypothalamic-pituitary-thyroid

axis• Regulates TSH secretion• Leads to hormone production• House heating system

HYPOTHYROIDISM• Too little thyroid hormone

• Common problem

• Associated with pregnancy

• Symptoms:• Weight gain • Sluggishness• Fatigue • Depression • Cold intolerance

• Causes:• Previous inflammation of the thyroid gland• Autoimmune Thyroiditis

• Affects millions of Americans• Some people do not know it affects them

Pink: Normal ThyroidBlue: Hypothyroid

HYPERTHYROIDISM• Too much thyroid hormone.

• Symptoms: • Muscle weakness and/or fatigue • Anxiety • Trouble sleeping• Mood swings• Rapid heartbeat

• Causes: • Graves’ disease (autoimmune disorder)• Toxic nodular or multinodular goiters• Pregnancy

• Treatment: • Anti-thyroid medications • Radioactive iodine• Therapy • Surgery

• Doctor may also prescribe beta blockers.

Pink: HyperthyroidBlue: Normal Thyroid

THYROIDITIS

• An inflammatory process ongoing within the thyroid gland.

• Findings of hypo- or hyper- thyroidism.

• Several types: • Silent Thyroiditis• Hashimoto’s Thyroiditis• De Quervain’s Thyroiditis

THYROID CANCER• Common malignancy

• Types:• Anaplastic Thyroid Cancer• Medullary Thyroid Cancer• Follicular and/or Hurthle cell thyroid cancer• Papillary and/or Mixed Papillary/Follicular

Thyroid Cancer

• Treatment:• Radioactive Iodine• Thyroidectomy

• Most cases are very curable

• Vast majority has long term survival

GOITERS

• A mass will compress the trachea and esophagus

• Symptoms:• Coughing• Waking up from sleep, feeling like you

can’t breathe• Sensation that food is getting stuck in

the upper throat

• Treatment:• Thyroid hormone (pill form)• Surgical removal

SOLITARY THYROID NODULES• Lumps within a normal thyroid gland

• No symptoms

• Found by feeling a lump in the throat

• 95% of thyroid nodules are benign• Health actions: contact a health physician after

finding lump

• Majority can be cured• Statistics:

• 1 in 12-15 young women• 1 in 40 young men• At least 1 thyroid nodule:

• 50% of 50 year olds• 60% of 60 year olds• 70% of 70 year olds

SCIENTIFIC JOURNALOVERACTIVE THYROID GLANDS PUT

PATIENTS AT INCREASED RISK FOR DEVELOPING AF (ATRIAL FIBRILLATION)

• Data • Joint 15th International Congress of Endocrinology • 14th European Congress of Endocrinology Meeting

• Christian Selmer, MD • Used 525,100 patients in a study of the relationship between thyroid dysfunction

and the risk of atrial fibrillation.

• Cumulative Incidence Plots and Poisson Regression Models • Measured TSH in the blood

• Subclinical Hypothyroidism --> lower risk for AF

• Subclinical Hyperthyroidism --> significant risk factor for AF

REFERENCES

• Endocrine Today. (2015). Overactive thyroid glands put patients at increased risk for developing AF. Retrieved from http://www.healio.com

• Sargis MD, PhD, R. M. (2015). Thyroid Gland Overview. Retrieved from http://www.endocrineweb.com

• Thyroid gland. (2015). Society for Endocrinology. Retrieved from http://www.yourhormones.info

• WebMD. (2015). Understanding Thyroid Problems – the Basics. Retrieved from http://www.webmd.com

• What Is the Role of Negative Feedback in the Endocrine System. (2015). Conjencture Corporation. Retrieved from http://www.wisegeek.com

• Better Health Channel. (2015). State Government of Victoria. Retrieved from http://www.betterhealth.vic.gov.au