Thyroid hormone is a hormone produced by the thyroid gland, which is located in the neck. It plays a crucial role in regulating metabolism, growth, and development in the body. The accurate description of thyroid hormone is that it binds to receptors on the inside of the cell (option D).

Here is a detailed explanation:

Thyroid hormone production:
- The thyroid gland produces two main hormones: thyroxine (T4) and triiodothyronine (T3).
- These hormones are synthesized by the follicular cells of the thyroid gland, which take up iodine from the bloodstream and combine it with the amino acid tyrosine to produce T4 and T3.
- T4 is the inactive form of the hormone, while T3 is the active form.

Transport and conversion:
- Once synthesized, T4 and T3 are released into the bloodstream and transported to target tissues throughout the body.
- The majority of thyroid hormone in the blood is in the form of T4, while T3 is present in smaller amounts.
- T4 can be converted to T3 by enzymes in various tissues, including the liver, kidneys, and other peripheral tissues.

Thyroid hormone receptors:
- Thyroid hormone exerts its effects by binding to nuclear receptors, known as thyroid hormone receptors (TRs), inside the cells.
- TRs are found in the nucleus of target cells and act as transcription factors, regulating gene expression.
- When thyroid hormone binds to TRs, it initiates a series of molecular events that lead to changes in gene expression, ultimately affecting cellular processes such as metabolism, growth, and development.

Function of thyroid hormone:
- Thyroid hormone affects almost every cell in the body and is essential for normal growth and development, as well as maintaining metabolic homeostasis.
- It increases the basal metabolic rate, promoting the consumption of oxygen and energy production in cells.
- Thyroid hormone is also involved in the regulation of body temperature, heart rate, and digestion.

In conclusion, thyroid hormone binds to receptors on the inside of the cell, specifically nuclear receptors, to exert its effects on gene expression and cellular processes.