Increased testicular size

Increased testicular size is found in males where a subject has abnormally large testicles. Normal testicular size in human is compared to body weight 0.08%. Testicular size correlates with tubular size, function and spermatogenesis. 

Testicular enlargement may have several causes and may also be highly associated with hypothyroidism (see bellow). Hypothyroid prepubertal testis may present a preponderance of tubular compartment with early onset of spermatogenesis and no increase in the number of Leydig cells. Adult testis, however, may present fibrosis and hyalinization of tubular walls, fibroblastic proliferation, peritubular and interstitial fibrosis with sparse Leydig cells, as well as reduction of tubular diameter, interstitial edema and tubular basal membrane stickiness.

Measurement in the living adult is done in two basic ways: comparing the testicle with ellipsoids of known sizes (orchidometer) or measuring the length, depth and width with a ruler, a pair of calipers or ultrasound imaging. In healthy adult humans, average testicular volume is 18 cm³ per testis, with normal size ranging from 12 cm³ to 30 cm³. The average testicle size after puberty measures up to around 5 cm in length, 2 in breadth x 3 cm in height. 

Thyroid disorders, Hypothyroidism

A thyroid disease is a medical condition impairing the function of the thyroid. The thyroid hormone T3 (triiodothyronine) is likely to represent a major hormonal signal to Sertoli cell proliferation during testicular development, and ultimately affecting the establishment of the adult Sertoli cell population. When thyroid gland doesn’t produce enough thyroid hormone (hypothyroidism), it is associated with enlarged testicles. 

Longer the hypothyroidism persists, the greater is the degree of damage to the testicles.