Subclinical hypothyroidism: summary of evidence in 2014 – Swiss Med Wkly. 2014 – free full-text
Because the symptoms of low thyroid overlap with those of Fibromyalgia and EDS (see The Fibromyalgia-Thyroid Connection), it may be worth checking thyroid levels to see if this might be contributing to the severity of symptoms.
My thyroid tests were on the low side of “normal”, but I’m blessed with a wonderful doctor who let me try supplementing with Armour thyroid based on my symptoms, not just my numbers.
Within days, I felt some relief from the worst of the heavy achiness, dull fatigue, and mental stupor I’d been plagued by. Even better – and unexpectedly – it also lifted my depression.
Armour thyroid tablets are desiccated pig thyroid with both T3 & T4, while the common prescription medication, levothyroxine, is only T4 and leaves it to the body to convert some of it to T3.
I tried the much cheaper generic levothyroxine, but it seemed to leave me shaky and weak in the afternoons (like after drinking too much coffee). When I switched to Armour, I finally experienced the benefits: a slight increase in energy, a slight easing of pain, and a lift of my mood.
Subclinical hypothyroidism, which is defined as elevated thyroid-stimulating hormone (TSH) levels with free thyroxine concentrations within the reference range, is a common disorder that increases with age and affects up to 18% of the elderly, with a higher prevalence in women compared to men
Prospective data have shown an increased risk of coronary heart disease events, heart failure, and cardiovascular mortality among affected adults.
Conflicting results have been found on the association between subclinical hypothyroidism and cognitive impairment, depression and the risk of fractures.
Management strategies including screening and treatment of subclinical hypothyroidism are still controversial,
Subclinical hypothyroidism is biochemically defined as elevated levels of thyroid-stimulating hormone (TSH) with normal levels of free thyroxine (fT4), while controversies exist on the limits of the TSH reference range.
The prevalence of subclinical hypothyroidism is large and ranges between 3% and 18% in the adult population, with women, elderly persons, and iodine sufficient populations being affected more often.
Cardiovascular risk and heart failure
Thyroid hormones are well known to act on the heart and vasculature, and the impact of subclinical thyroid dysfunction on the cardiovascular system has been an important topic of research in recent years.
Subclinical hypothyroidism can lead to impaired systolic and diastolic cardiac function as well as vascular dysfunction with increased vascular stiffness and endothelial dysfunction.
Musculoskeletal system and functional capacity
Persons with subclinical hypothyroidism more often suffer from weakness and myalgia, and reduced muscle strength has been shown in these individuals.
Confirming this hypothesis, beneficial effects of levothyroxine replacement on strength measurements and cardiopulmonary exercise performance have been demonstrated.
A possible mechanism for the lower exercise capacity could be higher oxygen requirements during exercise in people with subclinical hypothyroidism as well as a possible association with anaemia.
High TSH levels as seen in hypothyroidism have been shown to directly affect bone metabolism through
- inhibition of osteoclast formation and survival,
- osteoblast differentiation and
- expression of collagen type 1.
An association between subclinical hypothyroidism and mood disorders including depression and increased anxiety, as well as a reduced quality of life have been suggested,
Other clinical implications
The influence of overt hypothyroidism on gastrointestinal mobility with symptoms such as constipation are well known.