What are the symptoms of hypothyroidism?

The ability of Hypothyroidism to mimic a number of medical conditions originates in the vast functions of the thyroid hormones, which are absent in this case.

The functions of thyroid hormones include modulation of carbohydrate, protein and fat metabolism, vitamin utilization, mitochondrial function, digestive process, muscle and nerve activity, blood flow, oxygen utilization, hormone secretion and sexual and reproductive health to mention some. Thus, when the thyroid hormone content gets out of balance, systems covering the whole body are affected, and that's why hypothyroidism can look like other diseases. Conversely, sometimes other conditions can be mistaken for hypothyroidism.

Adults

In adults, hypothyroidism is associated with the following symptoms:

Early symptoms

Fatigue (physical)
Cold intolerance, increased sensitivity to cold
Constipation
Weight gain
Depression (especially in the elderly)
Muscle cramps and joint pain
Thin, Brittle fingernails
Thin, brittle hair
Paleness

Late symptoms

Slowed speech and a hoarse, breaking voice. Deepening of the voice can also be noticed.
Dry puffy skin, especially on the face
Thinning of the outer third of the eyebrows
Abnormal menstrual cycles (Specifically Menorrhagia)

More severe symptoms

Heat intolerance, increased sensitivity to heat
Impaired memory
Impaired cognitive function (brain fog) and inattentiveness
Urticaria (hives)
Migraine headaches
A slow heart rate with ECG changes including low voltage signals. Diminished cardiac output and decreased contractility.
Reactive(or post-prandial) hypoglycemia[8]
Pericardial effusions may occur.
Pleural effusion may occur.
Sluggish reflexes
hair loss
very low blood pressure
Anemia caused by impaired hemoglobin synthesis (decreased EPO levels), impaired intestinal iron and folate absorption or B12 deficiency from pernicious anemia
anxiety/panic attacks
difficulty swallowing
syncope (passing out)
dizziness
Shortness of breath with a shallow and slow respiratory pattern.
Impaired ventilatory responses to hypercapnia and hypoxia.
Increased need for sleep
Osteopenia or Osteoporosis
Irritability and mood instability
Yellowing of the skin due to impaired conversion of beta-carotene to vitamin A
Impaired renal function with decreased GFR.
Thin, fragile or absent cuticles
Elevated serum cholesterol
Acute psychosis (myxedema madness) is a rare presentation of hypothyroidism
Decreased libido
Myxedema coma (thyroid comna)
Decreased sense of taste and smell (late, less common symptoms)
Puffy face, hands and feet (late, less common symptoms)

Pediatric

Hypothyroidism in pediatric patients can cause the following additional symptoms:

short stature
mental retardation if present at birth, and untreated.

Severity

The severity of hypothyroidism varies widely. Some have few overt symptoms, others with moderate symptoms can be mistaken for having other diseases and states. Advanced hypothyroidism may cause severe complications including cardiovasular and psychiatric myxedema.