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June 14, 2021 | Farah Jassawalla

Muscle Weakness And Low Blood Pressure

Your body’s vital functions are assessed by a group of medical signs adequately termed as ‘vital signs.’ Among this group of four to six medical indications, one is blood pressure. Blood pressure refers to the force exerted by the blood on the walls of the circulatory system.

The most extensively studied condition related to blood pressure is hypertension; a rise in blood pressure. However, low blood pressure or hypotension requires due attention as well. This is so because low blood pressure is vaguely defined and often misinterpreted.

Statistics

Statistically speaking, the number of people with hypertension outnumber those with hypotension. Low blood pressure is often defined in vague terms with no definitive values.

To elaborate; if your blood pressure drops from 120/80mmHg (the standard levels), your blood pressure has technically been ‘lowered.’ However, you aren’t bound to experience general symptoms of hypotension.

Physicians have standardized hypotension levels at 90/60mmHg. Although it’s important to understand that your body’s compensatory mechanisms can limit the symptoms of hypotension to an almost non-existent extent.

How Do You Measure Blood Pressure?

Blood pressure is defined as the pressure exerted by the blood on the walls of the circulatory vessels, primarily the arteries. It’s usually expressed in terms of mmHg.

It is measured when your heart beats and in rest periods between each heartbeat. The measurement of your blood pumping through your arteries when the ventricles of the heart squeeze is called systolic pressure or systole. The measurement for the periods of rest is called diastolic pressure, or diastole.

  • The upper value is the systolic value. Systole is defined as the pressure exerted by the blood on the walls of the arteries after ventricular contraction. The systolic pressure is usually higher than the diastolic pressure.
  • The lower value is the diastolic value. Diastole is defined as the pressure exerted by the blood on the walls of the ventricles before ventricular contraction. The diastolic pressure is usually lower than the systolic pressure.

Muscle Weakness and Hypotension

Common symptoms associated with low blood pressure include:

  • Fatigue
  • Dizziness
  • Fainting (Syncope)
  • Blurred Vision
  • Nausea

These symptoms are descriptive of the primal consequence of inadequate blood flow; limited oxygen transport to vital organs and structures. To put this into context, your brain consumes 15% or 750mm of blood in a single circulatory cycle. If this flow is reduced even slightly, you’ll feel lightheaded.

Myasthenia or muscle weakness is a condition in itself manifested in certain disorders, diseases, or conditions. Hypotension and myasthenia coexist in certain conditions such as Addison’s Disease where ACTH deficiency causes reduced blood pressure and inadvertently causes muscle weakness.

General Descriptive Guidelines

 

Hypotension (in mmHg)

Associated Symptoms

90/60mmHg

Lightheadedness, Dizziness

80/60mmHg

Nausea, Vomiting

70/50mmHg

Blurry vision, muscle weakness

60/45mmHg

Sleepiness, Confusion

50/35mmHg

Coma, Death

It is important to understand that the values mentioned in the aforementioned table are relative. Symptoms of low blood pressure are variable from one person to the next.

When your blood pressure falls below 120/80mmHg, your body goes into compensatory systems. If the compensatory mechanisms are adequate enough, symptoms of low blood pressure won’t manifest until much later.

What Is ACTH?

Adrenocorticotropic hormone (ACTH) is one of six hormones secreted by the anterior pituitary gland. ACTH is principally involved in regulating cortisol levels in the body’s circulation.

The Hypothalamic-Pituitary-Adrenal Axis (HPA) is the body’s principal neuroendocrine pathway. The HPA axis stimulates one gland after the next to stimulate the body in response to mood, sexuality, digestion, and immune responses - basically, functions pertaining to the use of cortisol.

When Does the Body Release ACTH?

A better question would be, when does your body require cortisol? Cortisol is a hormone-regulated by the human body in conditions related to stress and in part related to the circadian rhythm.

The hormone is chiefly produced and stored in the adrenal gland. However, it is stimulated via the neuroendocrine pathways of the HPA axis. Under stressful conditions, the hypothalamus is stimulated to release corticotropin hormone.

This hormone stimulates the anterior pituitary gland to release ACTH which then further stimulates the adrenal gland to release cortisol from its cortex.

Conditions Associated With ACTH

  • Primary, Secondary, and Tertiary Adrenal Insufficiency
  • Cushing’s Disease
  • Addison’s Disease
  • Nelson’s Syndrome
  • West’s Syndrome
  • Carcinomas and Tumors of the Pituitary Gland
  • Critical Illnesses Related to Corticosteroid Insufficiency

Addison’s Disease

Addison’s disease affects men and women equally. An estimated 1 in 100,000 people living in the United States suffer from Addison’s disease; the extent of the condition is albeit variable from one patient to the next.

For context, around 40 to 60 people per million of the general population. However, there are several cases of Addison’s disease that go undiagnosed making the overall numbers difficult to estimate entirely.

Addison’s disease can potentially affect individuals of any age but usually occurs in individuals between 30-50 years of age. Addison’s disease was first identified in medical literature in 1855 by a physician named Thomas Addison.

The disease, also known as primary adrenal insufficiency, is a condition wherein the adrenal glands fail to produce sufficient (if any) amounts of cortisol.

The disease can turn life-threatening in cases of Addisonian Crisis -  when the symptoms of Addison’s Disease reach an unbearable extent (severe physical stress after major operations, infections, and illnesses).

Common symptoms of Addison’s Disease include:

  • Fatigue, exhaustion, and lack of energy
  • Unintentional Weight Loss (often rapid and dysmorphic)
  • Hyperpigmentation
  • Abdominal Pain
  • Nausea and Vomiting
  • Easily Irritable and Mental Discomfort
  • Headache
  • Increased Thirst (Polydipsia)
  • Low Blood Pressure
  • Muscle Weakness and Myasthenia

ACTH and Addison’s Disease

ACTH deficiency is a condition manifested by decreased or absent production of adrenocorticotropic hormone by the pituitary gland.

Addison’s disease caused by ACTH deficiency is a secondary cause of adrenal insufficiency.

Secondary adrenal insufficiency is often correlated in blood tests and leads to an affirmative diagnosis for hypoadrenalism. ACTH deficiency is a disorder that usually starts during adulthood although a few cases have begun during childhood.

Manifestations include:

  • Low blood sugar levels (hypoglycemia)
  • Low sodium levels (hyponatremia)
  • High potassium levels (hyperkalemia)

Blood Tests for Addison’s Disease

Myasthenia, Hypotension and Addison’s Disease

Addison’s disease is a metabolic condition related to adrenal insufficiency. The signs and symptoms of Addison’s disease are variable from one person to the next. However, in certain conditions (such as adrenal failure), your body experiences a condition known as Addisonian Crisis.

How do myasthenia and myalgia relate to adrenal insufficiency? And how does low blood pressure relate to both of them? One theory suggests that abnormal weight loss leads to low blood pressure and muscle wasting or muscle spasms.

Another theory suggests that low sodium intake related to increased thirst is responsible for irregular heartbeats and muscle wasting or muscle spasms.

Wrap Up

Hypotension is an often misunderstood medical condition that manifests in the form of lightheadedness and dizziness. However, abnormally low blood pressure levels may lead to a plethora of signs and symptoms including myalgia and myasthenia.

Addison’s disease presents as a triad between low ACTH levels, low blood pressure, and muscle wasting or muscle pain. Some patients of Addison’s disease often go several years without being properly diagnosed until their condition is exasperated in an Addisonian crisis.

Consult your doctor if you feel lightheaded, nauseous, or dizzy often. If your condition correlates with abnormal weight loss, your physician might order an ACTH level blood test to confirm Addison’s disease.

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Farah Jassawalla

Farah Jassawalla is a graduate of the Lahore School of Economics. She is also a writer, and a healthcare enthusiast, having closely observed case studies while working with Lahore's thriving general physicians at their clinics.