Hypothyroidism and slow metabolism are related. The pituitary gland in the brain is responsible for sleep, food cravings, stress and sex/thyroid hormones. It regulates thyroid hormones.

From:

https://www.ncbi.nlm.nih.gov/pmc…

Thyroid hormone (TH) is required for normal development as well as regulating metabolism in the adult. The thyroid hormone receptor (TR) isoforms, α and β, are differentially expressed in tissues and have distinct roles in TH signaling. Local activation of thyroxine (T4), to the active form, triiodothyronine (T3), by 5′-deiodinase type 2 (D2) is a key mechanism of TH regulation of metabolism. D2 is expressed in the hypothalamus, white fat, brown adipose tissue (BAT), and skeletal muscle and is required for adaptive thermogenesis. The thyroid gland is regulated by thyrotropin releasing hormone (TRH)…