Skin Morphology of Thyroidectomized Rats

Abstract

Abstract. We induced hypothyroidism in rats by conducting a thyroidectomy (TD) and investigated subsequent changes in the morphology of the skin, especially that of the epidermis and hair follicles. The 6 rats in the TD group seemed less active than the 3 rats in the control group and had cold, dry paws. All of the rats in the TD group exhibited retarded hair growth 12 weeks after surgery. Histologically, all of the rats in the TD group exhibited epidermal thinning from 12 weeks after surgery. Many hair follicles were in the telogen phase: the bulbs and papillae were involuted and had migrated towards the epidermis. Hair follicle atrophy involving thinning of the outer root sheath and the inner root sheath was often observed. The immunoreactivities of antithyroid hormone receptors a and b in the outer root sheaths of 5 of the TD rats were weaker than those of control rats. Cell proliferation in hair follicles of TD rats was weaker than in follicles of control rats 4 weeks after surgery. It is suggested that decreased expression of TRs and decreased cell proliferation activity in the hair follicles of rats is associated with a lack of thyroid hormone and results in retardation of hair growth.Key words: Hair follicle; hypothyroidism; thyroid hormone receptors; thyroidectomy.Hypothyroidism is a common cause of alopecia in humans and animals, especially dogs. 8,12,13 Thyroid hormone affects organs throughout the body because it regulates the activity of enzymes and proteins that participate in metabolism at the cellular level. In the human hair follicle, the thyroid hormone receptor (TR) participates in hair development.1,2 However, little research has been conducted on TRs and hair in animals or on the pathologic mechanism responsible for alopecia caused by hypothyroidism.Thyroidectomized animals are widely used to study hypothyroidism and thyroid hormone function. Although there are many reports on the effects of thyroidectomy (TD) on organs such as the anterior pituitary, liver, and kidneys, 7,14 little research has been conducted on the effects of TD on the skin. In this study, we induced hypothyroidism in rats by removing both lobes of the thyroid and investigated the subsequent morphologic changes in the skin, especially those in the epidermis and hair follicles. Materials and MethodsNine female Wistar rats (7 weeks old, 170-200 g) were kept under normal housing conditions (21uC 6 1uC, 50-60% humidity, light from 6:00 a.m. to 6:00 p.m.) with free access to food and water. Six rats were thyroidectomized (TD group) under diethyl ether as previously described, 20 and 3 rats underwent a sham operation (control group). Thyroidectomized rats were given drinking water containing 1% CaCl 2 to maintain calcium balance because the parathyroid gland was removed together with the thyroid gland. At 4, 8, 12, 16, and 32 weeks after surgery, skin samples were obtained under ether anesthesia from the dorsal trunk of the animals. The skin was repeatedly sampled from the same animal. Dorsal trunk skin was classified into five p...

Endothelial Functioning and Hemodynamic Parameters in Rats with Subclinical Hypothyroid and the Effects of Thyroxine Replacement

“…Upon gross inspection, the SCH rats seemed less active than the control rats and had dry fur. These results are the same as those of previous studies[ 33 , 41 , 42 ]. Body weights were improved in the SCH+T4 treatment groups ( Fig 1 ).…”

Effect of subclinical hypothyroidism on the skeletal system and improvement with short-term thyroxine therapy

“…The rats with SCH were less active and had dryer fur than the control rats, and body weights were significantly lower in the SCH group than in the control group (Figure 1 ). These results were similar to those of previous studies [ 22 – 25 ]. At the end of the 3-month study period, we found that body weights increased in the SCH+T4 treatment groups (Figure 1 ).…”

Biophysical parameters of rats’ skin after the administration of methimazole

“…Changes similar to those in human and canine hypothyreosis, including skin drying, inhibiting cell proliferation in hair follicles, telogenisation and follicular atrophy, disabling hair regrowth, as well as epidermal thinning can also be observed in rats. However, histopathological changes can be noted only after 12 weeks from removing the thyroid gland, and, contrary to what is observed in humans and dogs, no alopecia or hair thinning occurs in rats (38). In our experiment, the changes in the tested parameters in females were noted as early as 7 d after hypothyroidism induction.…”