Function and Role of Thyroid Hormones

The thyroid influences many of the body’s organs. A healthy, well-functioning thyroid gland is essential to the body’s overall well-being. Thyroid hormones protect against cardiovascular disease, cognitive impairment and memory loss, fatigue, and weight gain.

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Some of the roles of T3 (triiodothyronine) and/or T4 (thyroxine) include the following:

• Regulate metabolism
• Promote oxygen delivery to tissue
• Slow down or speeds up heart rate
• Regulate body temperature
• Influence speed of food moving through digestive tract
• Affect brain function

Symptoms of Thyroid Deficiency

• Fatigue
• Increased sensitivity to cold
• Irregular menstrual cycles
• Infertility
• Hoarse voice
• Thinning hair
• Slowed heart rate
• Weight gain
• Constipation
• Depression/anxiety
• Cognitive issues/memory problems

Causes of Suppressed Thyroid Hormones

Thyroid hormones can be suppressed by:

• Stress
• Depression
• Weight gain
• Leptin resistance
• Insulin resistance
• DM
• Low T
• Female
• Toxins
• Autoimmune
• FE DEF Anemia, Ferritin <70 or RDW>15

Indications for Treating Subclinical Hypothyroidism

• Elevated TSH (Thyroid Stimulating Hormone)
• Prevention of cardiovascular disease
• Low T3 levels
• Increased metabolism
• Memory/cognitive function
• Optimization of health

References: 

https://www.verywellhealth.com/armour-thyroid-for-hypothyroidism-3233291

https://www.webmd.com/drugs/2/drug-154794/np-thyroid-oral/details

Possible Side-effects of Thyroid Treatment

While side-effects are rarely seen with standard doses, the following side-effects are possible:

• Tremor/nervousness 
• Irritability
• Headache
• Insomnia
• Sweating
• Palpitations
• Tachycardia

Low Thyroid and the Heart

Low thyroid leads to heart disease:

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• Decreased cardiac output
• Increased systemic vascular resistance
• Decreased arterial compliance
• atherosclerosis
• Impaired cardiac muscle relaxation 
• Decreased heart rate
• Decreased stroke volume
• Hypothyroidism is associated with ischemic heart disease and increased cardiovascular mortality.

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Treatment leads to the protection of the heart and an improvement in: 

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• LDL cholesterol
• Total cholesterol
• Triglycerides
• Hypertension
• Diastolic dysfunction
• Heart rate and heart rate variability in exercise
• Improved cardiac contractility and stroke volume
• Delays progression of atherosclerosis

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References: 

Udovcic M, Pena RH, Patham B, Tabatabai L, Kansara A. Hypothyroidism and the Heart. Methodist Debakey Cardiovasc J. 2017 Apr-Jun;13(2):55-59. doi: 10.14797/mdcj-13-2-55. PMID: 28740582; PMCID: PMC5512679.