Wants to know how to Hypothyroidism Diagnosis ? Hypothyroidism is a condition of the thyroid gland that affects the production of thyroid hormones, important hormones in the regulation of metabolism. TSH is a hormone released from the pituitary gland in the brain. This hormone stimulates the thyroid gland into secreting thyroxine and thyroid hormone. For hypothyroidism diagnosis – the TSH test is the primary test used for the diagnosis and management of hypothyroidism.