Underactive thyroid gland condition causes underproduction of thyroid hormones, which leads to several undesired biological changes and results in many sign and symptoms.
The clinical experts evaluate the different factors involved in underactive thyroid gland functioning.
The primary finding is faulty immune system response which initiates progression of autoimmune disease in the thyroid gland.
However, certain epidemiological factors also deregulate thyroid hormone secretion, such as global warming, which is one of the major cause of increased incidence of underactive thyroid gland condition, as in hot climate thyroid hormones release is decreased due to reduced secretion of TSH (thyroid a stimulating hormone).
Overview of Thyroid Gland and its Hormonal Release
The thyroid gland is a butterfly-shaped endocrine gland located in the frontal area of the neck. The thyroid gland secretes hormones including T3, T4, and calcitonin.
Both T3 and T4 enhances the basal metabolic rate of the body and produces more energy. Calcitonin produced by C-cells plays a major role in calcium metabolism and bone health maintenance.
Overproduction and underproduction of these thyroid hormones are clinically denoted as hyperthyroidism and hypothyroidism respectively and provide many abnormal physiological consequences. 
The signs and symptoms associated with underactive thyroid:
The characteristic features of hypothyroidism lead to a decreased rate of body metabolism and causing low energy, tiredness, or constipation.  In a progressive hypothyroidism stage, the following are the common symptoms of hypothyroidism: 
• Fatigue after short exhaustive work
• Put on weight
• Extremely sensitive to cold temperature
• Pain in joints and muscle
• Irregular bowel movement or constipation
• Hair fall
• Dull and dry hair
• Irregular menstrual cycle with heavy bleeding
• Problem to conceive
• Memory impairment
• Slow heart rate
SPECIFIC CHARACTERISTICS OF HASHIMOTO'S
• Abnormal sensation of pharynx
• Hoarseness the
• A sore throat
Hypothyroidism related complications include enlargement of goiter in the neck region, hyperlipidemia, reduced mental functioning, myxedema, and complication in pregnancy (decreased neurological growth of the fetus).
rief description of Hashimoto’s thyroiditis
Hashimoto’s is an organ-specific autoimmune disease that mediates through T-cells and affects the thyroid and genes.
Genetics play a crucial contributory factor in developing complexity in Hashimoto’s condition.  Different identified genes are responsible for Hashimoto’s disease such as CTLA-4 A49G single nucleotide polymorphisms gene, interleukin-1 receptor antagonist gene, and SEP (selenoprotein) S gene.
Although, the detail contributory mechanism of these genetic factors in Hashimoto’s disease is yet to be discovered. 
The above-mentioned hypothyroidism related symptoms usually do not appear in Hashimoto’s disease, but some of these symptoms are apparent in Hashimoto’s disease. 
I’ve read the colitis and black cumin article in your site. I wanted to say that I completely cured my allergic runny nose by eating nigella sativa.
Nigella sativa is known to cure every disease among Muslim people. Because our Prophet (peace be upon him) said so nearly 1400 years ago. Here is the translation of the hadith:
“Use this black seed regularly, because it is a cure for every disease, except death.” (Sunan Ibn Majah)