Which one of the following human hormones contains iodine?

Thyroxin (T4) is the primary human hormone that contains iodine. Iodine is an essential trace element required for the synthesis of thyroid hormones [1][t2]. Specifically, thyroxin contains four atoms of iodine per molecule, which is why it is often referred to as T4 [t7]. The thyroid gland traps iodine from the bloodstream and processes it into these hormones to regulate the body's basal metabolic rate, growth, and development [c1][t5]. A deficiency in dietary iodine leads to decreased thyroxin synthesis, resulting in conditions like goitre, characterized by a swollen neck [c1][t2]. In contrast, adrenalin (epinephrine) is an amine hormone derived from tyrosine but does not contain iodine [t6]. Progesterone is a steroid hormone derived from cholesterol, and oxytocin is a peptide hormone consisting of a chain of amino acids; neither of these requires iodine for their structure or function [t6][t8].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 6: Control and Coordination > Do You Know? > p. 110